Er5Ni2Bi crystallizes in the tetragonal I4/mcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to four equivalent Ni(1) and two equivalent Bi(1) atoms to form distorted ErNi4Bi2 octahedra that share corners with six equivalent Er(1)Ni4Bi2 octahedra, corners with sixteen equivalent Er(2)Ni3Bi2 square pyramids, and faces with eight equivalent Er(2)Ni3Bi2 square pyramids. The corner-sharing octahedral tilt angles range from 0-51°. In the second Er site, Er(2) is bonded to three equivalent Ni(1) and two equivalent Bi(1) atoms to form distorted ErNi3Bi2 square pyramids that share corners with four equivalent Er(1)Ni4Bi2 octahedra, corners with twelve equivalent Er(2)Ni3Bi2 square pyramids, edges with seven equivalent Er(2)Ni3Bi2 square pyramids, faces with two equivalent Er(1)Ni4Bi2 octahedra, and  a faceface with one Er(2)Ni3Bi2 square pyramid. The corner-sharing octahedral tilt angles range from 42-61°. Ni(1) is bonded in a 8-coordinate geometry to two equivalent Er(1) and six equivalent Er(2) atoms. Bi(1) is bonded in a distorted q6 geometry to two equivalent Er(1) and eight equivalent Er(2) atoms.
Er5Ni2Bi crystallizes in the tetragonal I4/mcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to four equivalent Ni(1) and two equivalent Bi(1) atoms to form distorted ErNi4Bi2 octahedra that share corners with six equivalent Er(1)Ni4Bi2 octahedra, corners with sixteen equivalent Er(2)Ni3Bi2 square pyramids, and faces with eight equivalent Er(2)Ni3Bi2 square pyramids. The corner-sharing octahedral tilt angles range from 0-51°. All Er(1)-Ni(1) bond lengths are 2.96 Å. Both Er(1)-Bi(1) bond lengths are 3.34 Å. In the second Er site, Er(2) is bonded to three equivalent Ni(1) and two equivalent Bi(1) atoms to form distorted ErNi3Bi2 square pyramids that share corners with four equivalent Er(1)Ni4Bi2 octahedra, corners with twelve equivalent Er(2)Ni3Bi2 square pyramids, edges with seven equivalent Er(2)Ni3Bi2 square pyramids, faces with two equivalent Er(1)Ni4Bi2 octahedra, and  a faceface with one Er(2)Ni3Bi2 square pyramid. The corner-sharing octahedral tilt angles range from 42-61°. There are two shorter (2.82 Å) and one longer (2.89 Å) Er(2)-Ni(1) bond length. Both Er(2)-Bi(1) bond lengths are 3.26 Å. Ni(1) is bonded in a 8-coordinate geometry to two equivalent Er(1) and six equivalent Er(2) atoms. Bi(1) is bonded in a distorted q6 geometry to two equivalent Er(1) and eight equivalent Er(2) atoms.