Crystal structure and magnetic properties of the uranium germanide U5Ge4

The crystal structure of the uranium germanide U5Ge4 was determined and refined from single crystal X-ray diffraction data to R = 0.043, Rw = 0.054. U5Ge4 crystallizes in the hexagonal Ti5Ga4 (P6(3)/mcm) structure type (filled up Mn5Si3 type) with the following lattice parameters: a = 8.744(4) Angstrom and c = 5.863(2) Angstrom. Investigation of neighbouring compositions, using X-ray powder diffraction refinements and microprobe analysis, revealed that the binary compound U5Ge4 is in equilibrium with the other binary UGe (Thin type) and U metal dissolving 3% of germanium, whatever the annealing temperature in the range of 1000-1300 degrees C. These results rule out the existence of the binary compositions U5Ge3 and U7Ge, which were previously reported. Magnetic measurements on an annealed polycrystalline powder sample of U5Ge4 indicate nearly temperature independent paramagnetic behaviour down to 2 K. (C) 1997 Elsevier Science S.A.