THE TERNARY URANIUM TRANSITION-METAL PHOSPHIDES UV5P3, UCR5P3, AND UMN5P3

The title compounds were prepared from prereacted samples of the elemental components by arc-melting. UCr5P3 was also obtained from a tin flux. UV5P3 and UCr5P3 crystallize with a new structure type, which was determined from X-ray data of a twinned crystal of UCr5P3: P2(1)/m, a = 959.1(2), b = 370.95(6), c = 696.7(1) pm, beta = 100.05(3)degrees, Z = 2, R = 0.030 for 827 structure factors and 29 variable parameters. UMn5P3 is isotypic with YCoP3. The structure was refined to a residual of R = 0.054 for 455 structure factors and 28 variables. UCr5P3, has a relatively high, almost temperature independent paramagnetic susceptibility as is frequently observed for metallic uranium compounds. The crystal structures of these phosphides are discussed together with those of other phosphides and silicides of similar composition.