Er3Pm is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded to eight Er(1,1) and four equivalent Pm(1) atoms to form ErPm4Er8 cuboctahedra that share corners with four equivalent Pm(1)Er12 cuboctahedra; corners with fourteen equivalent Er(1)Pm4Er8 cuboctahedra; edges with six equivalent Pm(1)Er12 cuboctahedra; edges with twelve Er(1,1)Pm4Er8 cuboctahedra; faces with four equivalent Pm(1)Er12 cuboctahedra; and faces with sixteen Er(1,1,1)Pm4Er8 cuboctahedra. In the second Er site, Er(1) is bonded to eight Er(1,1) and four equivalent Pm(1) atoms to form ErPm4Er8 cuboctahedra that share corners with four equivalent Pm(1)Er12 cuboctahedra; corners with fourteen Er(1,1,1)Pm4Er8 cuboctahedra; edges with six equivalent Pm(1)Er12 cuboctahedra; edges with twelve Er(1,1)Pm4Er8 cuboctahedra; faces with four equivalent Pm(1)Er12 cuboctahedra; and faces with sixteen Er(1,1,1)Pm4Er8 cuboctahedra. In the third Er site, Er(1) is bonded to eight Er(1,1) and four equivalent Pm(1) atoms to form ErPm4Er8 cuboctahedra that share corners with four equivalent Pm(1)Er12 cuboctahedra; corners with fourteen Er(1,1,1)Pm4Er8 cuboctahedra; edges with six equivalent Pm(1)Er12 cuboctahedra; edges with twelve Er(1,1)Pm4Er8 cuboctahedra; faces with four equivalent Pm(1)Er12 cuboctahedra; and faces with sixteen Er(1,1,1)Pm4Er8 cuboctahedra. Pm(1) is bonded to twelve Er(1,1,1) atoms to form PmEr12 cuboctahedra that share corners with six equivalent Pm(1)Er12 cuboctahedra; corners with twelve Er(1,1,1)Pm4Er8 cuboctahedra; edges with eighteen Er(1,1,1)Pm4Er8 cuboctahedra; faces with eight equivalent Pm(1)Er12 cuboctahedra; and faces with twelve Er(1,1,1)Pm4Er8 cuboctahedra.
Er3Pm is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded to eight Er(1,1) and four equivalent Pm(1) atoms to form ErPm4Er8 cuboctahedra that share corners with four equivalent Pm(1)Er12 cuboctahedra; corners with fourteen equivalent Er(1)Pm4Er8 cuboctahedra; edges with six equivalent Pm(1)Er12 cuboctahedra; edges with twelve Er(1,1)Pm4Er8 cuboctahedra; faces with four equivalent Pm(1)Er12 cuboctahedra; and faces with sixteen Er(1,1,1)Pm4Er8 cuboctahedra. There are a spread of Er(1)-Er(1,1) bond distances ranging from 3.54-3.64 Å. There are two shorter (3.56 Å) and two longer (3.60 Å) Er(1)-Pm(1) bond lengths. In the second Er site, Er(1) is bonded to eight Er(1,1) and four equivalent Pm(1) atoms to form ErPm4Er8 cuboctahedra that share corners with four equivalent Pm(1)Er12 cuboctahedra; corners with fourteen Er(1,1,1)Pm4Er8 cuboctahedra; edges with six equivalent Pm(1)Er12 cuboctahedra; edges with twelve Er(1,1)Pm4Er8 cuboctahedra; faces with four equivalent Pm(1)Er12 cuboctahedra; and faces with sixteen Er(1,1,1)Pm4Er8 cuboctahedra. There are a spread of Er(1)-Er(1,1) bond distances ranging from 3.54-3.64 Å. There are two shorter (3.56 Å) and two longer (3.60 Å) Er(1)-Pm(1) bond lengths. In the third Er site, Er(1) is bonded to eight Er(1,1) and four equivalent Pm(1) atoms to form ErPm4Er8 cuboctahedra that share corners with four equivalent Pm(1)Er12 cuboctahedra; corners with fourteen Er(1,1,1)Pm4Er8 cuboctahedra; edges with six equivalent Pm(1)Er12 cuboctahedra; edges with twelve Er(1,1)Pm4Er8 cuboctahedra; faces with four equivalent Pm(1)Er12 cuboctahedra; and faces with sixteen Er(1,1,1)Pm4Er8 cuboctahedra. There are two shorter (3.56 Å) and two longer (3.60 Å) Er(1)-Pm(1) bond lengths. Pm(1) is bonded to twelve Er(1,1,1) atoms to form PmEr12 cuboctahedra that share corners with six equivalent Pm(1)Er12 cuboctahedra; corners with twelve Er(1,1,1)Pm4Er8 cuboctahedra; edges with eighteen Er(1,1,1)Pm4Er8 cuboctahedra; faces with eight equivalent Pm(1)Er12 cuboctahedra; and faces with twelve Er(1,1,1)Pm4Er8 cuboctahedra.