A new family of rare earth-rhodium-tin intermetallic compounds, with the representative formula (RE)Rh~Sn~, has been synthesized in single crystal form. The compounds containing the heavier rare earths are superconducting and those with the lighter rare earths are generally magnetic. The compound ErRh Sn 36 exhibits reentrant superconductivity with T~= 0.97 K and Tm = 0.57 K as determined from ac magnetic susceptibility measurements. The synthesis and X-ray characterization of the series are described and the results of electrical resistivity, upper critical magnetic field, magnetic susceptibility, specific heat and neutron scattering measurements on the Er compound are given.

Two systems of ternary transition metal phosphides with the ordered Fe2P-type hexagonal structure are reported. They have the general formula MRuP and MOsP, in which M can be Ti, Zr, or Hf. An onset of the superconducting transition temperature as high as 13.0 K is reported for the ZrRuP compound.Many ternary transition metal phosphides with the general formula MM'P and the ordered Fe2P-type hexagonal structure (C22) (1) are known: TiMnP, MnNiP, FeNiP, CoNiP, MoNiP, WNiP, MnRuP, CrRhP, MnRhP, CrPdP, and CaAgP (2-7). M6ssbauer studies and x-ray intensity measurements show that in general M and M' are metal elements with M occupying the 3(g) positions of the space group P62m, and M' occupying the 3(f) positions. As a rule, M is to the left of M' in the periodic table. In the case that M and M' have similar atomic sizes, there is a possibility that a slight disorder may occur. For example, in the FeNiP compounds, 25-30% of the 3(g) positions are occupied by Ni. The crystallographic ordering is reported to be very sensitive to the heat treatment of the samples, and it is possible that the ordering may effect the magnetic properties of the compounds (6,(8)(9)(10).With the presence of the 3d transition metals Cr, Mn, Fe, Co, or Ni, most of the compounds reported were ordered ferromagnetically, and no superconductivity was reported in this particular group of ternary transition metal phosphides.During the study of the Zr-Ru-P ternary system, many samples had been found to become superconducting above 10 K. Because there are no superconducting transition temperatures (TCs) reported above 6 K in the related binary systems (11), and because most ternary phosphide phases are reported with the 1-1-1 composition,* ZrRuP was made; it was found to form the ordered Fe2P-type structure, with an onset of superconductivity as high as 13.0 K. EXPERIMENTAL DETAILS All samples were prepared from transition metals with purities of 99.9% and red phosphorus with a purity of better than 99.999%. Mixtures of the powders were pressed into small pellets and sintered between 800 and 1200°C in sealed quartz tubes under an argon atmosphere. Some samples were synthesized by making the binary RuP and OsP compounds first. After the measurements, all sintered compounds were arcmelted under an argon atmosphere in a Zr-gettered arc furnace and then annealed between 800 and 1200°C.Powder x-ray diffraction data were taken on a GE XTD-6The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertlsement" in accordance with 18 U. S. C. §1734 solely to indicate this fact. 3132 diffractometer (CuKa radiation), equipped with a diffractedbeam crystal monochrometer, at a scanning rate of 0.20 in 20 per minute. Line intensities were determined by weighing paper tracings of the diffracted peaks, and the program "Lazy Pulverix" was used to calculate the line intensities (12). Superconducting transition temperatures were obtained from low frequency (20-Hz) ac magnetic susceptib...

A new system of high-temperature superconductors is reported. The compounds, Mo(6 - x)A(x)S(6) where A is Cu, Zn, Mg, Ag, Cd, Sn, or Pb, are rhombohedral with a approximately 6.5 angstroms and approximately 90 degrees . The transition temperatures range from approximately 2.5 degrees K for the Cd compound to approximately 13 degrees K for the Pb compound.

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A new group of ternary borides has been found that show either ferromagnetism or superconductivity. Their general formula is MRh4B4 where M is a transition or rare-earth element. Their superconducting transition temperatures range from approximately 2.5 K for the Sm compound to approximately 12 K for the Lu compound. In the past, the superconducting transition temperatures of borides have always been rather low. The highest values, in the vicinity of 8 K, were reached with pseudobinary molybdenum borides which were metastable and had to be splat cooled (1).We have now discovered an entirely new group of superconducting borides which are true ternary compounds, as opposed to the previously known pseudobinary phases. These new compounds have the general formula MRh4B4 (where M is a three or four valent transition element), and their superconducting transition temperatures, by far the highest yet observed for any borides, are given in Table 1. Transition temperatures were a few tenths of a degree higher when the samples contained an excess of RhB and the values given are for compositions MRh4B4 + 2 [RhB]. This is only the second true ternary system of high-temperature superconductors found thus far. The first was that of the double molybdenum sulphides (2) originally reported by Chevrel et al. (3).In contrast to the double sulphides, those compounds in this new superconducting system which have high transition temperatures are the very ones formed with elements which by themselves are not superconducting above 0.1 K. However, some striking analogies to the double sulphides have also been observed. When M is a magnetic rare-earth element such as erbium or thulium the transition temperature is fairly high, even higher than that of the corresponding molybdenum sulphides (4) or selenides (5). And yet, in this new system there is now a sudden switch to magnetism upon replacing erbium by holmium, a phenomenon never known before (see Table 2).The two crystallographic systems are quite different from each other. Whereas the sulphides are rhombohedral, the new system is tetragonal (6). For the sulphides, values of the metallic radii were not at all critical, but now only values between 1.70 A and 1.82 A for M in MRh4B4 are able to form this new phase. Again, in contrast to the sulphides, the electron/atom ratio is of decisive importance here, as shown by comparison of the yttrium and lutetium compounds to the thorium compound. Whereas the rhombohedral crystal structure of the molybdenum sulphides may be closely related to a more symmetrical