Crystal and Magnetic Structure of New Ternary Uranium Intermetallics: U3TiX5(X=Ge, Sn)

New compounds with the formula U3TiX5have been synthesized forX=Ge, Sn. The crystal structure of U3TiGe5has been refined from single crystal X-ray diffraction data toR(F)=0.032,Rw=0.037, and was found to crystallize with the hexagonal U3TiSb5structure type, witha=8.495(1) ? andc=5.711(1) ?. Isotypism was found from X-ray powder diffraction analysis for the stannide U3TiSn5, witha=9.200(2) ? andc=6.128(3) ?. Magnetic susceptibility measurements carried out on polycrystalline powder samples reveal ferromagnetic type ordering atTC=76 and 65 K for U3TiGe5and U3TiSn5, respectively. Neutron powder diffraction studies of U3TiGe5show that the uranium magnetic moments have two components: a ferromagnetic component (MF=0.9MU Bat 1.4 K) along thecaxis and a triangular component (MT=0.4MUBat 1.4 K) in the hexagonal plane antiferromagnetically ordered along thecaxis.