Synthesis, structure, and magnetic and electronic properties of Cs2Hg2USe5

The compound Cs2Hg2USe5 was obtained from the solid-state reaction of U, HgSe, Cs2Se3, Se, and CsI at 1123 K. This material crystallizes in a new structure type in space group P2/n of the monoclinic system with a cell of dimensions a=10.276(6) A, b=4.299(2) A, c=15.432(9) A, β=101.857(6) A, and V=667.2(6) A3. The structure contains ∞2[Hg2USe5] layers separated by Cs atoms. Within the layers are distorted HgSe4 tetrahedra and regular USe6 octahedra. In the temperature range of 25-300 K Cs2Hg2USe5 displays Curie-Weiss paramagnetism with μeff=3.71(2) μB. The compound exhibits semiconducting behavior in the [010] direction; the conductivity at 298 K is 3x10-3 S/cm. Formal oxidation states of Cs/Hg/U/Se may be assigned as +1/+2/+4/- 2, respectively. - Graphical abstract: View of the crystal structure of Cs2Hg2USe5.