Synthesis, Structure, and Physical Properties of Mixed Valent Mo₂SbS₂, the First Superconducting Antimonide-Sulfide

We identified a new ternary molybdenum antimonide-sulfide, Mo 2 SbS 2 . Black, needle-shaped crystals of Mo 2 SbS 2 can be synthesized by reacting stoichiometric amounts of the elements at 850 °C for 7 days with I 2 (<2 wt %) as the transporting reagent; however, the crystals of Mo 2 SbS 2 are too small for a single-crystal structure investigation. Therefore, the crystal structure of Mo 2 SbS 2 was analyzed by powder X-ray diffraction using Rietveld refinements. The compound crystallizes in a monoclinic system (space group P 2 1 / m, a = 6.50920(7) Å, b = 3.18231(4) Å, c = 9.3548(1) Å, β = 105.4430(8)°, Z = 2). The title compound is isostructural with Mo 2 S 3; and the Mo−Mo, Mo−Sb, and Mo−S distances are comparable with those in MoSb 2 S. The results from the Seebeck coefficient and magnetic susceptibility measurements and electronic band structure calculations suggest metallic behavior. The band structure of Mo 2 SbS 2 exhibits van Hove singularities hinting at superconductivity, which was subsequently confirmed via magnetic susceptibility measurements.