Crystal Structure and Superconductivity of Tetragonal and Monoclinic CePr OBiS.

CePr OBiS powders and CePrOBiS single crystals were synthesized and their structure and superconductive properties were examined by X-ray diffraction, X-ray absorption, electronic resistivity, and magnetization. While PrOBiS was found to be in a monoclinic phase with one-dimensional Bi-S zigzag chains showing no superconductive transition above 0.1 K, CeOBiS was in a tetragonal phase with two-dimensional Bi-S planes showing zero resistivity below 1.3 K. In the range x = 0.3-0.9 in CePr OBiS, both monoclinic and tetragonal phases were formed together with zero resistivity up to a maximum temperature of 2.2 K. A CePrOBiS single crystal, which showed both zero resistivity and a decrease in magnetization at ∼2.4 K, presented a tetragonal structure. Short Bi-S bonding in flat two-dimensional Bi-S planes and mixed Ce/Ce were characteristic features of the CePrOBiS single crystal, which presumably triggered its superconductivity.