Er3Sm is alpha La-derived structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to four equivalent Er(1), four equivalent Er(2), and four equivalent Sm(1) atoms to form ErSm4Er8 cuboctahedra that share corners with twelve equivalent Er(1)Sm4Er8 cuboctahedra, edges with eight equivalent Er(1)Sm4Er8 cuboctahedra, edges with eight equivalent Er(2)Sm4Er8 cuboctahedra, edges with eight equivalent Sm(1)Er12 cuboctahedra, faces with four equivalent Er(2)Sm4Er8 cuboctahedra, faces with four equivalent Sm(1)Er12 cuboctahedra, and faces with ten equivalent Er(1)Sm4Er8 cuboctahedra. In the second Er site, Er(2) is bonded to eight equivalent Er(1) and four equivalent Sm(1) atoms to form ErSm4Er8 cuboctahedra that share corners with four equivalent Er(2)Sm4Er8 cuboctahedra, corners with eight equivalent Sm(1)Er12 cuboctahedra, edges with eight equivalent Er(2)Sm4Er8 cuboctahedra, edges with sixteen equivalent Er(1)Sm4Er8 cuboctahedra, faces with four equivalent Er(2)Sm4Er8 cuboctahedra, faces with six equivalent Sm(1)Er12 cuboctahedra, and faces with eight equivalent Er(1)Sm4Er8 cuboctahedra. Sm(1) is bonded to four equivalent Er(2) and eight equivalent Er(1) atoms to form SmEr12 cuboctahedra that share corners with four equivalent Sm(1)Er12 cuboctahedra, corners with eight equivalent Er(2)Sm4Er8 cuboctahedra, edges with eight equivalent Sm(1)Er12 cuboctahedra, edges with sixteen equivalent Er(1)Sm4Er8 cuboctahedra, faces with four equivalent Sm(1)Er12 cuboctahedra, faces with six equivalent Er(2)Sm4Er8 cuboctahedra, and faces with eight equivalent Er(1)Sm4Er8 cuboctahedra.
Er3Sm is alpha La-derived structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to four equivalent Er(1), four equivalent Er(2), and four equivalent Sm(1) atoms to form ErSm4Er8 cuboctahedra that share corners with twelve equivalent Er(1)Sm4Er8 cuboctahedra, edges with eight equivalent Er(1)Sm4Er8 cuboctahedra, edges with eight equivalent Er(2)Sm4Er8 cuboctahedra, edges with eight equivalent Sm(1)Er12 cuboctahedra, faces with four equivalent Er(2)Sm4Er8 cuboctahedra, faces with four equivalent Sm(1)Er12 cuboctahedra, and faces with ten equivalent Er(1)Sm4Er8 cuboctahedra. All Er(1)-Er(1) bond lengths are 3.55 Å. All Er(1)-Er(2) bond lengths are 3.53 Å. All Er(1)-Sm(1) bond lengths are 3.53 Å. In the second Er site, Er(2) is bonded to eight equivalent Er(1) and four equivalent Sm(1) atoms to form ErSm4Er8 cuboctahedra that share corners with four equivalent Er(2)Sm4Er8 cuboctahedra, corners with eight equivalent Sm(1)Er12 cuboctahedra, edges with eight equivalent Er(2)Sm4Er8 cuboctahedra, edges with sixteen equivalent Er(1)Sm4Er8 cuboctahedra, faces with four equivalent Er(2)Sm4Er8 cuboctahedra, faces with six equivalent Sm(1)Er12 cuboctahedra, and faces with eight equivalent Er(1)Sm4Er8 cuboctahedra. All Er(2)-Sm(1) bond lengths are 3.55 Å. Sm(1) is bonded to four equivalent Er(2) and eight equivalent Er(1) atoms to form SmEr12 cuboctahedra that share corners with four equivalent Sm(1)Er12 cuboctahedra, corners with eight equivalent Er(2)Sm4Er8 cuboctahedra, edges with eight equivalent Sm(1)Er12 cuboctahedra, edges with sixteen equivalent Er(1)Sm4Er8 cuboctahedra, faces with four equivalent Sm(1)Er12 cuboctahedra, faces with six equivalent Er(2)Sm4Er8 cuboctahedra, and faces with eight equivalent Er(1)Sm4Er8 cuboctahedra.