Uranium I 5900 Synthesis and Crystal Structure of Zn 2 [(UO 2 ) 3 (SeO 4 ) 5 ](H 2 O) 17 . -Single crystals of the title compound are synthesized by evaporation of aqueous solutions of (UO2)(NO3)2, ZnO, and H2SeO4 at room temperature. Zn2[(UO2)3(SeO4)5](H2O)17 crystallizes in the orthorhombic space group Pbca with Z = 8. The structure is based on [(UO2)3(SeO4)5] 4sheets formed by corner-sharing UO7 pentagonal bipyramids and SeO 4 groups. -(KRIVOVICHEV*, S. V.; KAHLENBERG, V.; J. Alloys Compd. 389 (2005) 1-2, 55-60; Inst. Mineral. Petrogr., Leopold-Franzens-Univ., A-6020 Innsbruck, Austria; Eng.) -W. Pewestorf