Syntheses of new rare-earth rhodium borocarbides

Single crystals of a new quaternary compound, ErRh₂B₂C, were obtained by the flux growth method using molten copper as a flux. The extracted crystals show golden-coloured luster and a maximum size of approximately 1 × 1 × 0.02 mm³. This compound has tetragonal symmetry and appeared to be a derivative of the ThCr₂Si₂-type; the lattice parameters are a = 0.36848(2) nm and c = 1.05520(3) nm. The electrical resistivity parallel to the a-b plane of the crystal decreases with decreasing temperature. The residual resistance ratio ρ (273 K)/ρ (1.5 K) is 1.38. No superconductivity was observed down to 1.5 K. The search for similar types of new compounds was performed using the arc-melting synthetic method. The new quaternary RRh₂B₂C compounds are obtained for R = La – Er (except Eu) and Y. The phase stability of RRh₂B₂C was discussed.