ErFeAl crystallizes in the orthorhombic Amm2 space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 16-coordinate geometry to one Er(1), three equivalent Er(2), three equivalent Fe(1), four equivalent Fe(2), one Al(3), two equivalent Al(1), and two equivalent Al(2) atoms. In the second Er site, Er(2) is bonded in a 12-coordinate geometry to three equivalent Er(1), two equivalent Fe(2), three equivalent Fe(1), one Al(1), two equivalent Al(3), and four equivalent Al(2) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to three equivalent Er(1), three equivalent Er(2), two equivalent Fe(2), one Al(1), one Al(3), and two equivalent Al(2) atoms to form distorted FeEr6Al4Fe2 cuboctahedra that share corners with two equivalent Al(3)Er6Al4Fe2 cuboctahedra, corners with two equivalent Al(1)Er6Fe6 cuboctahedra, corners with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, corners with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with six equivalent Fe(1)Er6Al4Fe2 cuboctahedra, faces with two equivalent Fe(1)Er6Al4Fe2 cuboctahedra, faces with three equivalent Al(3)Er6Al4Fe2 cuboctahedra, faces with three equivalent Al(1)Er6Fe6 cuboctahedra, faces with six equivalent Fe(2)Er6Al2Fe4 cuboctahedra, and faces with six equivalent Al(2)Er6Al4Fe2 cuboctahedra. In the second Fe site, Fe(2) is bonded to two equivalent Er(2), four equivalent Er(1), two equivalent Fe(1), two equivalent Fe(2), and two equivalent Al(1) atoms to form FeEr6Al2Fe4 cuboctahedra that share corners with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, corners with four equivalent Fe(1)Er6Al4Fe2 cuboctahedra, corners with four equivalent Al(3)Er6Al4Fe2 cuboctahedra, corners with six equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with two equivalent Fe(2)Er6Al2Fe4 cuboctahedra, edges with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with two equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with two equivalent Al(3)Er6Al4Fe2 cuboctahedra, faces with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with four equivalent Al(1)Er6Fe6 cuboctahedra, and faces with six equivalent Fe(1)Er6Al4Fe2 cuboctahedra. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent Er(2), four equivalent Er(1), two equivalent Fe(1), and four equivalent Fe(2) atoms to form AlEr6Fe6 cuboctahedra that share corners with two equivalent Al(3)Er6Al4Fe2 cuboctahedra, corners with four equivalent Fe(1)Er6Al4Fe2 cuboctahedra, corners with four equivalent Al(1)Er6Fe6 cuboctahedra, corners with eight equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with two equivalent Al(1)Er6Fe6 cuboctahedra, edges with four equivalent Al(3)Er6Al4Fe2 cuboctahedra, faces with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with six equivalent Fe(1)Er6Al4Fe2 cuboctahedra, and faces with eight equivalent Fe(2)Er6Al2Fe4 cuboctahedra. In the second Al site, Al(2) is bonded to two equivalent Er(1), four equivalent Er(2), two equivalent Fe(1), two equivalent Al(2), and two equivalent Al(3) atoms to form AlEr6Al4Fe2 cuboctahedra that share corners with four equivalent Fe(1)Er6Al4Fe2 cuboctahedra, corners with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, corners with four equivalent Al(1)Er6Fe6 cuboctahedra, corners with six equivalent Fe(2)Er6Al2Fe4 cuboctahedra, edges with two equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with two equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with two equivalent Al(1)Er6Fe6 cuboctahedra, faces with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with four equivalent Al(3)Er6Al4Fe2 cuboctahedra, and faces with six equivalent Fe(1)Er6Al4Fe2 cuboctahedra. In the third Al site, Al(3) is bonded to two equivalent Er(1), four equivalent Er(2), two equivalent Fe(1), and four equivalent Al(2) atoms to form AlEr6Al4Fe2 cuboctahedra that share corners with two equivalent Al(1)Er6Fe6 cuboctahedra, corners with four equivalent Fe(1)Er6Al4Fe2 cuboctahedra, corners with four equivalent Al(3)Er6Al4Fe2 cuboctahedra, corners with eight equivalent Fe(2)Er6Al2Fe4 cuboctahedra, edges with two equivalent Al(3)Er6Al4Fe2 cuboctahedra, edges with four equivalent Al(1)Er6Fe6 cuboctahedra, faces with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with six equivalent Fe(1)Er6Al4Fe2 cuboctahedra, and faces with eight equivalent Al(2)Er6Al4Fe2 cuboctahedra.
ErFeAl crystallizes in the orthorhombic Amm2 space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 16-coordinate geometry to one Er(1), three equivalent Er(2), three equivalent Fe(1), four equivalent Fe(2), one Al(3), two equivalent Al(1), and two equivalent Al(2) atoms. The Er(1)-Er(1) bond length is 3.15 Å. There is one shorter (3.24 Å) and two longer (3.27 Å) Er(1)-Er(2) bond lengths. There is one shorter (3.09 Å) and two longer (3.16 Å) Er(1)-Fe(1) bond lengths. There are two shorter (3.09 Å) and two longer (3.15 Å) Er(1)-Fe(2) bond lengths. The Er(1)-Al(3) bond length is 3.12 Å. Both Er(1)-Al(1) bond lengths are 3.11 Å. Both Er(1)-Al(2) bond lengths are 3.12 Å. In the second Er site, Er(2) is bonded in a 12-coordinate geometry to three equivalent Er(1), two equivalent Fe(2), three equivalent Fe(1), one Al(1), two equivalent Al(3), and four equivalent Al(2) atoms. Both Er(2)-Fe(2) bond lengths are 3.01 Å. There are two shorter (3.11 Å) and one longer (3.24 Å) Er(2)-Fe(1) bond length. The Er(2)-Al(1) bond length is 3.03 Å. Both Er(2)-Al(3) bond lengths are 3.18 Å. There are two shorter (3.16 Å) and two longer (3.21 Å) Er(2)-Al(2) bond lengths. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to three equivalent Er(1), three equivalent Er(2), two equivalent Fe(2), one Al(1), one Al(3), and two equivalent Al(2) atoms to form distorted FeEr6Al4Fe2 cuboctahedra that share corners with two equivalent Al(3)Er6Al4Fe2 cuboctahedra, corners with two equivalent Al(1)Er6Fe6 cuboctahedra, corners with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, corners with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with six equivalent Fe(1)Er6Al4Fe2 cuboctahedra, faces with two equivalent Fe(1)Er6Al4Fe2 cuboctahedra, faces with three equivalent Al(3)Er6Al4Fe2 cuboctahedra, faces with three equivalent Al(1)Er6Fe6 cuboctahedra, faces with six equivalent Fe(2)Er6Al2Fe4 cuboctahedra, and faces with six equivalent Al(2)Er6Al4Fe2 cuboctahedra. Both Fe(1)-Fe(2) bond lengths are 2.51 Å. The Fe(1)-Al(1) bond length is 2.57 Å. The Fe(1)-Al(3) bond length is 2.67 Å. Both Fe(1)-Al(2) bond lengths are 2.71 Å. In the second Fe site, Fe(2) is bonded to two equivalent Er(2), four equivalent Er(1), two equivalent Fe(1), two equivalent Fe(2), and two equivalent Al(1) atoms to form FeEr6Al2Fe4 cuboctahedra that share corners with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, corners with four equivalent Fe(1)Er6Al4Fe2 cuboctahedra, corners with four equivalent Al(3)Er6Al4Fe2 cuboctahedra, corners with six equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with two equivalent Fe(2)Er6Al2Fe4 cuboctahedra, edges with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with two equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with two equivalent Al(3)Er6Al4Fe2 cuboctahedra, faces with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with four equivalent Al(1)Er6Fe6 cuboctahedra, and faces with six equivalent Fe(1)Er6Al4Fe2 cuboctahedra. There is one shorter (2.64 Å) and one longer (2.73 Å) Fe(2)-Fe(2) bond length. There is one shorter (2.62 Å) and one longer (2.77 Å) Fe(2)-Al(1) bond length. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent Er(2), four equivalent Er(1), two equivalent Fe(1), and four equivalent Fe(2) atoms to form AlEr6Fe6 cuboctahedra that share corners with two equivalent Al(3)Er6Al4Fe2 cuboctahedra, corners with four equivalent Fe(1)Er6Al4Fe2 cuboctahedra, corners with four equivalent Al(1)Er6Fe6 cuboctahedra, corners with eight equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with two equivalent Al(1)Er6Fe6 cuboctahedra, edges with four equivalent Al(3)Er6Al4Fe2 cuboctahedra, faces with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with six equivalent Fe(1)Er6Al4Fe2 cuboctahedra, and faces with eight equivalent Fe(2)Er6Al2Fe4 cuboctahedra. In the second Al site, Al(2) is bonded to two equivalent Er(1), four equivalent Er(2), two equivalent Fe(1), two equivalent Al(2), and two equivalent Al(3) atoms to form AlEr6Al4Fe2 cuboctahedra that share corners with four equivalent Fe(1)Er6Al4Fe2 cuboctahedra, corners with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, corners with four equivalent Al(1)Er6Fe6 cuboctahedra, corners with six equivalent Fe(2)Er6Al2Fe4 cuboctahedra, edges with two equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with two equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with two equivalent Al(1)Er6Fe6 cuboctahedra, faces with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with four equivalent Al(3)Er6Al4Fe2 cuboctahedra, and faces with six equivalent Fe(1)Er6Al4Fe2 cuboctahedra. There is one shorter (2.62 Å) and one longer (2.75 Å) Al(2)-Al(2) bond length. There is one shorter (2.63 Å) and one longer (2.75 Å) Al(2)-Al(3) bond length. In the third Al site, Al(3) is bonded to two equivalent Er(1), four equivalent Er(2), two equivalent Fe(1), and four equivalent Al(2) atoms to form AlEr6Al4Fe2 cuboctahedra that share corners with two equivalent Al(1)Er6Fe6 cuboctahedra, corners with four equivalent Fe(1)Er6Al4Fe2 cuboctahedra, corners with four equivalent Al(3)Er6Al4Fe2 cuboctahedra, corners with eight equivalent Fe(2)Er6Al2Fe4 cuboctahedra, edges with two equivalent Al(3)Er6Al4Fe2 cuboctahedra, edges with four equivalent Al(1)Er6Fe6 cuboctahedra, faces with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with six equivalent Fe(1)Er6Al4Fe2 cuboctahedra, and faces with eight equivalent Al(2)Er6Al4Fe2 cuboctahedra.