CHARACTERIZATION OF NOVEL TERNARY URANIUM SILICIDES AND GERMANIDES WITH THE U2MO3SI4 STRUCTURE TYPE IN THE U-(MO,W,V)-(SI,GE) SYSTEMS

Novel compounds, U2W3Si4, U(0)2Mo(3)Ge(4) and U2V3Ge4, have been synth esised by argon are melting, using the correct elemental compositions. The crystal structures of U2W3Si4 (a=6.847(5) Angstrom, b=6.858(1) An gstrom, c=6.767(9) Angstrom, beta=109.77(1)degrees) and of U2Mo3Ge4 (a =7.016(4) Angstrom, b=6.995(2) Angstrom, c=6.949 Angstrom, beta=110.21 (2)degrees) have been determined from single-crystal X-ray data. They have been shown to be isotypic with U2Mo3Si4 (a=6.876(3) Angstrom, b=6 .883(1) Angstrom, c=6.760(3) Angstrom, beta=109.79(2)degrees, space gr oup P2(1)/c, Z=2). From X-ray powder intensity data, U2V3Ge4 (a=6.986( 1) Angstrom, b=6.976(1) Angstrom, c=6.927(1) Angstrom, beta=109.94(2)d egrees) was found to crystallize in the same structure type. U2V3Ge4 i s ferromagnetic below T-c=60 K whereas U2W3Si4, U2Mo3Si4 and U2Mo2Ge4 do not show any ferromagnetic transition at low temperature.