Platinum-germanium ordering in UPtGe

The non-centrosymmetric structure of UPtGe was investigated by X-ray diffra ction on both powders and single crystals: EuAuGe type, Imm2, a = 432.86(5) , b = 718.81(8), c = 751.66(9) pm, wR(2) = 0.0738 for 399 F-2 values and 22 variables. The platinum and germanium atoms form two-dimensional layers of puckered Pt3Ge3 hexagons with short Pt-Ge intralayer distances of 252 and 253 pm. These condensed two-dimensionally infinite nets are interconnected to each other via weak Pt-Pt contacts with bond distances of 300 pm. The tw o crystallographically independent uranium atoms are situated above and bel ow the six-membered platinum-germanium rings. The U I atoms have six closer germanium neighbors while the U2 atoms have six closer platinum neighbors. The group-subgroup relation with the KHg2 type structure is presented. (C) 2001 Editions scientifiques et medicales Elsevier SAS. All rights reserved .