Crystal and magnetic structure of new ternary uranium intermetallics: U3TiX5 (X = Ge, Sn)

New compounds with the formula U3TiX5 have been synthesized for X = Ge, Sn, The crystal structure of U3TiGe5 has been refined from single crystal X-ra y diffraction data to R(F) = 0.032, R-w = 0.037, and was found to crystalli ze with the hexagonal U3TiSb5 structure type, with a = 8.495(1) Angstrom an d c = 5.711(1) Angstrom. Isotypism was found from X-ray powder diffraction analysis for the stannide U3TiSn5, with a = 9.200(2) Angstrom and c = 6.128 (3) A. Magnetic susceptibility measurements carried out on polycrystalline powder samples reveal ferromagnetic type ordering at T-C = 76 and 65 K for U3TiGe5 and U3TiSn5, respectively, Neutron powder diffraction studies of U3 TiCe5 show that the uranium magnetic moments have two components: a ferroma gnetic component (M-F = 0.9 mu(B) at 1.4 K) along the c axis and a triangul ar component (M-T = 0.4 mu(B) at 1.4 K) in the hexagonal plane antiferromag netically ordered along the c axis. (C) 1999 Academic Press.