Crystal structure and superstructure of URh1.6As1.9

Abstract A novel ternary intermetallic compound was observed in the U-Rh-As system. The composition of this compound corresponds to URh1.62As1.85 as determined by scanning electron microscopy analysis and X-ray diffraction study. It crystallizes at room temperature in a CaBe2Ge2-type structure. The crystal structure was refined from single-crystal diffractometer data to residual R = 0.07. A careful analysis of the precession films indicates a super structure with the following relation between the vectors of the supercell and the subcell: a = 2a0, − 2b0, b = 2a0 + 2b0, c = 2c0. From the single-crystal diffractometer data refinement, a model is proposed for the super-structure based on a specific arrangement of rhodium and arsenic voids in this compound. The superstructure is both compositional and displacive.