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 P 2/n of the monoclinic system with a cell of dimensions a =10.276(6) Å, b =4.299(2) Å, c =15.432(9) Å, β =101.857(6) Å, and V =667.2(6) Å3. The structure contains View the MathML source∞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 3×10−3 S/cm. Formal oxidation states of Cs/Hg/U/Se may be assigned as +1/+2/+4/− 2, respectively.