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Heat-capacity measurements of a 39 microg MgB2 single crystal in fields up to 14 T and below 3 K allow the determination of the low-temperature linear term of the specific heat, its field dependence, and its anisotropy. Our results are compatible with two-band superconductivity, the band carrying the smaller gap being isotropic, that carrying the larger gap having an anisotropy of approximately 5. Three different upper critical fields are thus needed to describe the superconducting state of MgB2.

CeNiGe 3 , crystallizing in the orthorhombic SmNiGe 3 -type crystal structure, was studied by means of dc and ac magnetic susceptibility, magnetization, electrical resistivity, magnetoresistivity, Hall effect, and specific-heat measurements. The compound orders antiferromagnetically at T N ϭ5.5 K due to the presence of well localized 4 f magnetic moments, which are partly screened via a Kondo-like mechanism. The electrical behavior is governed by an interplay of Ruderman-Kittel-Kasuya-Yosida and Kondo interactions modified by crystal-field effects. The Kondo temperature is of similar magnitude as T N , and the overall crystal electric field splitting is of the order of 160 K. The low-temperature specific heat exhibits some enhancement indicating the formation of moderate-heavy quasiparticles in the antiferromagnetic state. The specific variation with applied magnetic field of the main physical characteristics of CeNiGe 3 points at a complex magnetic structure of the compound in the ordered region.

RPdBi (R = Er, Ho, Gd, Dy, Y, Nd) compounds were studied by means of x-ray diffraction, magnetic susceptibility, electrical resistivity, magnetoresistivity, thermoelectric power and Hall effect measurements, performed in the temperature range 1.5-300 K and in magnetic fields up to 12 T. These ternaries, except diamagnetic YPdBi, exhibit localized magnetism of R 3+ ions, and order antiferromagnetically at low temperatures (TN = 2-13 K). The transport measurements revealed behavior characteristic of semimetals or narrow-band semiconductors. Both, electrons and holes contribute to the conductivity with dominant role of p-type carriers. The Hall effect of ErPdBi is strongly temperature and magnetic field dependent, reflecting complex character of the underlying electronic structures with multiple electron and hole bands. RPdBi, and especially DyPdBi, exhibit very good thermoelectric properties with a power factor coefficient P F ranging from 6 to 20 µWcm −1 K −2 .PACS numbers:

Four series of ternary compounds RPdSb ͑R =Y,Ho,Er͒, RPdBi ͑R =Nd,Y,Dy,Ho,Er͒, RPd 2 Sb ͑R =Y,Gd-Er͒, and RPd 2 Bi ͑R =Y,Dy-Er͒ were studied by means of magnetization, magnetic susceptibility, electrical resistivity, magnetoresistivity, thermoelectric power, and Hall effect measurements, performed in the temperature range 1.5-300 K and in magnetic fields up to 12 T. All these ternaries, except for diamagnetic Y-based phases, exhibit localized magnetism of R 3+ ions, and a few of them order antiferromagnetically at low temperatures ͑T N =2-14 K͒. The equiatomic compounds show half-metallic conductivity due to the formation of narrow gaps in their electronic band structures near the Fermi energy. Their Seebeck coefficient at room temperature is exceptionally high ͑S up to 200 V/K͒, being promising for thermoelectric applications. In contrast, all the 1:2:1 phases are semimetals and their thermoelectric power is much lower ͑maximum S of 10-25 V/K͒. The Hall effect in the compounds studied corroborates complex character of their electronic structure with multiple electron and hole bands with different temperature and magnetic field variations of carrier concentrations and their mobilities.