The structure of the binary germanide Pr 4 Ge 7 has been determined by single-crystal X-ray diffraction on a twinned crystal. It is an ordered vacancy derivative of the α-ThSi 2 type, Pearson symbol oS44, space group C222 1 , a = 6.007(2), b = 13.987(4), c = 12.009(4) Å, isotypic to the structure reported earlier for Nd 4 Ge 7. The cell parameters of seven other praseodymium germanides observed in samples annealed at 873 K were refined from powder X-ray diffraction data.

The crystal structure of a new ternary aluminide of refined composition Sc6Cu24.1(2)Al11.9(2) was solved by direct methods from X-ray powder diffraction data. It belongs to the cubic space group Im-3, Pearson symbol cI176-8, a = 13.5337(5) Å. The structure of Sc6Cu24.1Al11.9 may be described as a packing of 16-vertex coordination polyhedra of the Sc atoms, which form icosahedral clusters around the origin and the center of the body-centered unit cell. The voids at the centers of the clusters are filled by Cu4 tetrahedra, disordered between two possible orientations. The structure is closely related to the structure types Ru3Be17 and Ce6Au27.6Sn6.8.

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Isothermal sections of the phase diagrams were constructed at 1073 and 773 K for the Pr-Ag-Si system and at 873 K for the Y-Ag-Si system based on X-ray powder diffraction data. The crystal structures of two ternary compounds in the Pr-Ag-Si system were refined by the Rietveld method: PrAg 2 Si 2 , СeAl 2 Ga 2-type structure, Pearson symbol tI10, space group I4/mmm, unit-cell parameters a = 0.42084(1), c = 1.06735(2) nm at 1073 K and CeNi 2+x Sb 2-x-type structure, oI10, Immm, a = 0.42088(2), b = 0.42287(2), c = 1.06695(3) nm at 773 K; PrAgSi, LiBaSi-type structure, hP3, P-6m2, a = 0.42302(1), c = 0.41911(1) nm at 1073 K and LaPtSi-type structure, tI12, I4 1 md, a = 0.42087(2), c = 1.46432(8) nm at 773 K.