ErLa3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. Er(1) is bonded to four equivalent La(2) and eight equivalent La(1) atoms to form ErLa12 cuboctahedra that share corners with four equivalent Er(1)La12 cuboctahedra, corners with eight equivalent La(2)La8Er4 cuboctahedra, edges with eight equivalent Er(1)La12 cuboctahedra, edges with sixteen equivalent La(1)La8Er4 cuboctahedra, faces with four equivalent Er(1)La12 cuboctahedra, faces with six equivalent La(2)La8Er4 cuboctahedra, and faces with eight equivalent La(1)La8Er4 cuboctahedra. There are two inequivalent La sites. In the first La site, La(1) is bonded to four equivalent Er(1), four equivalent La(1), and four equivalent La(2) atoms to form LaLa8Er4 cuboctahedra that share corners with twelve equivalent La(1)La8Er4 cuboctahedra, edges with eight equivalent Er(1)La12 cuboctahedra, edges with eight equivalent La(1)La8Er4 cuboctahedra, edges with eight equivalent La(2)La8Er4 cuboctahedra, faces with four equivalent Er(1)La12 cuboctahedra, faces with four equivalent La(2)La8Er4 cuboctahedra, and faces with ten equivalent La(1)La8Er4 cuboctahedra. In the second La site, La(2) is bonded to four equivalent Er(1) and eight equivalent La(1) atoms to form LaLa8Er4 cuboctahedra that share corners with four equivalent La(2)La8Er4 cuboctahedra, corners with eight equivalent Er(1)La12 cuboctahedra, edges with eight equivalent La(2)La8Er4 cuboctahedra, edges with sixteen equivalent La(1)La8Er4 cuboctahedra, faces with four equivalent La(2)La8Er4 cuboctahedra, faces with six equivalent Er(1)La12 cuboctahedra, and faces with eight equivalent La(1)La8Er4 cuboctahedra.
ErLa3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. Er(1) is bonded to four equivalent La(2) and eight equivalent La(1) atoms to form ErLa12 cuboctahedra that share corners with four equivalent Er(1)La12 cuboctahedra, corners with eight equivalent La(2)La8Er4 cuboctahedra, edges with eight equivalent Er(1)La12 cuboctahedra, edges with sixteen equivalent La(1)La8Er4 cuboctahedra, faces with four equivalent Er(1)La12 cuboctahedra, faces with six equivalent La(2)La8Er4 cuboctahedra, and faces with eight equivalent La(1)La8Er4 cuboctahedra. All Er(1)-La(2) bond lengths are 3.68 Å. All Er(1)-La(1) bond lengths are 3.69 Å. There are two inequivalent La sites. In the first La site, La(1) is bonded to four equivalent Er(1), four equivalent La(1), and four equivalent La(2) atoms to form LaLa8Er4 cuboctahedra that share corners with twelve equivalent La(1)La8Er4 cuboctahedra, edges with eight equivalent Er(1)La12 cuboctahedra, edges with eight equivalent La(1)La8Er4 cuboctahedra, edges with eight equivalent La(2)La8Er4 cuboctahedra, faces with four equivalent Er(1)La12 cuboctahedra, faces with four equivalent La(2)La8Er4 cuboctahedra, and faces with ten equivalent La(1)La8Er4 cuboctahedra. All La(1)-La(1) bond lengths are 3.68 Å. All La(1)-La(2) bond lengths are 3.69 Å. In the second La site, La(2) is bonded to four equivalent Er(1) and eight equivalent La(1) atoms to form LaLa8Er4 cuboctahedra that share corners with four equivalent La(2)La8Er4 cuboctahedra, corners with eight equivalent Er(1)La12 cuboctahedra, edges with eight equivalent La(2)La8Er4 cuboctahedra, edges with sixteen equivalent La(1)La8Er4 cuboctahedra, faces with four equivalent La(2)La8Er4 cuboctahedra, faces with six equivalent Er(1)La12 cuboctahedra, and faces with eight equivalent La(1)La8Er4 cuboctahedra.