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

We identified a new ternary molybdenum antimonide-sulfide, Mo2SbS2. Black, needle-shaped crystals of Mo2SbS2 can be synthesized by reacting stoichiometric amounts of the elements at 850 °C for 7 days with I2 (<2 wt %) as the transporting reagent; however, the crystals of Mo2SbS2 are too small for a single-crystal structure investigation. Therefore, the crystal structure of Mo2SbS2 was analyzed by powder X-ray diffraction using Rietveld refinements. The compound crystallizes in a monoclinic system (space group P21/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 Mo2S3; and the Mo−Mo, Mo−Sb, and Mo−S distances are comparable with those in MoSb2S. The results from the Seebeck coefficient and magnetic susceptibility measurements and electronic band structure calculations suggest metallic behavior. The band structure of Mo2SbS2 exhibits van Hove singularities hinting at superconductivity, which was subsequently confirmed via magnetic susceptibility measurements.