Structure of Nb5(Gex,Sn1−x)2Ge, x = 0.25

Nb 5 Ge 1.5 Sn 1.5 , M r =751.45, tetragonal, I4/mcm, a=10.451 (1), c=5.1920 (7) A, V=567.0 (1) A 3 , Z=4, D x =8.80 Mg m -3 , λ(Mo Kα)=0.71069 A, μ=24.05 mm -1 , F(000)=1312, roomtemperature, final R=0.044, wR=0.042 for 245 [|Fo|>3σ(F o )] unique reflections. The title compound is isomorphous with W 5 Si 3 . The 16(k) and 4(a) sites are only occupied by Nb, and the 4(b) sites only by Ge