Synthesis, structure, and magnetic properties of Ba2Cu2US5

The alkaline-earth uranium chalcogenide Ba2Cu2US5 was obtained in a two-step reaction from BaS, Cu2S, and US2. Ba2Cu2US5 crystallizes in a new structure type in space group C2/m of the monoclinic system with two formula units in a cell of dimensions a=13.606(3) Å, b=4.0825(8) Å, c=9.3217(19) Å, and β=116.32(3)° (153 K). The structure consists of image layers separated by Ba atoms in bicapped trigonal-prismatic coordination. The two-dimensional image layer is built from US6 octahedra and CuS4 tetrahedra. The connectivity of the MSn polyhedra within the layer in the [001] direction is oct tet tet oct tet tet. A μeff value of 2.69(2) μB/U was obtained from the magnetic susceptibility data. No magnetic transition was observed for Ba2Cu2US5 down to 2 K.