Properties of Superconducting R₂O₂Bi (R = Y, Er) with Anti-ThCr₂Si₂-type Structure

A new family of bismuth compounds, R₂O₂Bi (R = Y, Ce and Er etc.) crystallized in the anti-ThCr₂Si₂-type structure where Bi ions form a square net, has attracted much attention because this family exhibits varous interesting ground states including antiferromagnetic (AFM) order, heavy fermion behavior and superconductivity (SC). We have investigated two compounds Ce₂O₂Bi and Er₂O₂Bi by measuring transport and magnetic properties, as well as specific heat. While Ce2O2Bi behaves as a Kondo lattice and experiences an antiferromagnetic (AFM) transition at T_N of about 6.7 K, Er₂O₂Bi is a superconductor with Tc of 1 K. A coexistence of AFM and SC is found. There is a correlationship between the oxygen content and Tc. This work offers a new candidate material for studying the interplay between SC and 4f electron magnetism.