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 12-coordinate geometry to three equivalent Er(2), one Fe(3), two equivalent Fe(1), two equivalent Fe(2), three equivalent Al(1), and four equivalent Al(2) atoms. In the second Er site, Er(2) is bonded in a 16-coordinate geometry to one Er(2), three equivalent Er(1), one Fe(1), two equivalent Fe(3), four equivalent Fe(2), two equivalent Al(2), and three equivalent Al(1) atoms. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Er(2), four equivalent Er(1), two equivalent Al(1), and four equivalent Al(2) atoms to form FeEr6Al6 cuboctahedra that share corners with two equivalent Fe(3)Er6Al2Fe4 cuboctahedra, corners with four equivalent Fe(1)Er6Al6 cuboctahedra, corners with four equivalent Al(1)Er6Al2Fe4 cuboctahedra, corners with eight equivalent Fe(2)Er6Al2Fe4 cuboctahedra, edges with two equivalent Fe(1)Er6Al6 cuboctahedra, edges with four equivalent Fe(3)Er6Al2Fe4 cuboctahedra, faces with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with six equivalent Al(1)Er6Al2Fe4 cuboctahedra, and faces with eight equivalent Al(2)Er6Al4Fe2 cuboctahedra. In the second Fe site, Fe(2) is bonded to two equivalent Er(1), four equivalent Er(2), two equivalent Fe(2), two equivalent Fe(3), and two equivalent Al(1) atoms to form distorted FeEr6Al2Fe4 cuboctahedra that share corners with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, corners with four equivalent Fe(1)Er6Al6 cuboctahedra, corners with four equivalent Al(1)Er6Al2Fe4 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 Fe(1)Er6Al6 cuboctahedra, faces with two equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with four equivalent Fe(3)Er6Al2Fe4 cuboctahedra, and faces with six equivalent Al(1)Er6Al2Fe4 cuboctahedra. In the third Fe site, Fe(3) is bonded to two equivalent Er(1), four equivalent Er(2), four equivalent Fe(2), and two equivalent Al(1) atoms to form distorted FeEr6Al2Fe4 cuboctahedra that share corners with two equivalent Fe(1)Er6Al6 cuboctahedra, corners with four equivalent Fe(3)Er6Al2Fe4 cuboctahedra, corners with four equivalent Al(1)Er6Al2Fe4 cuboctahedra, corners with eight equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with two equivalent Fe(3)Er6Al2Fe4 cuboctahedra, edges with four equivalent Fe(1)Er6Al6 cuboctahedra, faces with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with six equivalent Al(1)Er6Al2Fe4 cuboctahedra, and faces with eight equivalent Fe(2)Er6Al2Fe4 cuboctahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to three equivalent Er(1), three equivalent Er(2), one Fe(1), one Fe(3), two equivalent Fe(2), and two equivalent Al(2) atoms to form distorted AlEr6Al2Fe4 cuboctahedra that share corners with two equivalent Fe(3)Er6Al2Fe4 cuboctahedra, corners with two equivalent Fe(1)Er6Al6 cuboctahedra, corners with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, corners with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with six equivalent Al(1)Er6Al2Fe4 cuboctahedra, faces with two equivalent Al(1)Er6Al2Fe4 cuboctahedra, faces with three equivalent Fe(3)Er6Al2Fe4 cuboctahedra, faces with three equivalent Fe(1)Er6Al6 cuboctahedra, faces with six equivalent Fe(2)Er6Al2Fe4 cuboctahedra, and faces with six equivalent Al(2)Er6Al4Fe2 cuboctahedra. In the second Al site, Al(2) is bonded to two equivalent Er(2), four equivalent Er(1), two equivalent Fe(1), two equivalent Al(1), and two equivalent Al(2) atoms to form distorted AlEr6Al4Fe2 cuboctahedra that share corners with four equivalent Fe(3)Er6Al2Fe4 cuboctahedra, corners with four equivalent Al(1)Er6Al2Fe4 cuboctahedra, corners with four equivalent Al(2)Er6Al4Fe2 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 Fe(3)Er6Al2Fe4 cuboctahedra, faces with four equivalent Fe(1)Er6Al6 cuboctahedra, faces with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, and faces with six equivalent Al(1)Er6Al2Fe4 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 12-coordinate geometry to three equivalent Er(2), one Fe(3), two equivalent Fe(1), two equivalent Fe(2), three equivalent Al(1), and four equivalent Al(2) atoms. There is one shorter (3.27 Å) and two longer (3.28 Å) Er(1)-Er(2) bond lengths. The Er(1)-Fe(3) bond length is 3.03 Å. Both Er(1)-Fe(1) bond lengths are 3.18 Å. Both Er(1)-Fe(2) bond lengths are 3.02 Å. There are two shorter (3.12 Å) and one longer (3.16 Å) Er(1)-Al(1) bond length. There are two shorter (3.14 Å) and two longer (3.17 Å) Er(1)-Al(2) bond lengths. In the second Er site, Er(2) is bonded in a 16-coordinate geometry to one Er(2), three equivalent Er(1), one Fe(1), two equivalent Fe(3), four equivalent Fe(2), two equivalent Al(2), and three equivalent Al(1) atoms. The Er(2)-Er(2) bond length is 3.07 Å. The Er(2)-Fe(1) bond length is 3.21 Å. Both Er(2)-Fe(3) bond lengths are 3.09 Å. There are two shorter (3.06 Å) and two longer (3.08 Å) Er(2)-Fe(2) bond lengths. Both Er(2)-Al(2) bond lengths are 3.21 Å. There is one shorter (3.04 Å) and two longer (3.16 Å) Er(2)-Al(1) bond lengths. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Er(2), four equivalent Er(1), two equivalent Al(1), and four equivalent Al(2) atoms to form FeEr6Al6 cuboctahedra that share corners with two equivalent Fe(3)Er6Al2Fe4 cuboctahedra, corners with four equivalent Fe(1)Er6Al6 cuboctahedra, corners with four equivalent Al(1)Er6Al2Fe4 cuboctahedra, corners with eight equivalent Fe(2)Er6Al2Fe4 cuboctahedra, edges with two equivalent Fe(1)Er6Al6 cuboctahedra, edges with four equivalent Fe(3)Er6Al2Fe4 cuboctahedra, faces with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with six equivalent Al(1)Er6Al2Fe4 cuboctahedra, and faces with eight equivalent Al(2)Er6Al4Fe2 cuboctahedra. Both Fe(1)-Al(1) bond lengths are 2.73 Å. There are two shorter (2.63 Å) and two longer (2.68 Å) Fe(1)-Al(2) bond lengths. In the second Fe site, Fe(2) is bonded to two equivalent Er(1), four equivalent Er(2), two equivalent Fe(2), two equivalent Fe(3), and two equivalent Al(1) atoms to form distorted FeEr6Al2Fe4 cuboctahedra that share corners with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, corners with four equivalent Fe(1)Er6Al6 cuboctahedra, corners with four equivalent Al(1)Er6Al2Fe4 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 Fe(1)Er6Al6 cuboctahedra, faces with two equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, faces with four equivalent Fe(3)Er6Al2Fe4 cuboctahedra, and faces with six equivalent Al(1)Er6Al2Fe4 cuboctahedra. There is one shorter (2.50 Å) and one longer (2.86 Å) Fe(2)-Fe(2) bond length. There is one shorter (2.52 Å) and one longer (2.79 Å) Fe(2)-Fe(3) bond length. Both Fe(2)-Al(1) bond lengths are 2.63 Å. In the third Fe site, Fe(3) is bonded to two equivalent Er(1), four equivalent Er(2), four equivalent Fe(2), and two equivalent Al(1) atoms to form distorted FeEr6Al2Fe4 cuboctahedra that share corners with two equivalent Fe(1)Er6Al6 cuboctahedra, corners with four equivalent Fe(3)Er6Al2Fe4 cuboctahedra, corners with four equivalent Al(1)Er6Al2Fe4 cuboctahedra, corners with eight equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with two equivalent Fe(3)Er6Al2Fe4 cuboctahedra, edges with four equivalent Fe(1)Er6Al6 cuboctahedra, faces with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, faces with six equivalent Al(1)Er6Al2Fe4 cuboctahedra, and faces with eight equivalent Fe(2)Er6Al2Fe4 cuboctahedra. Both Fe(3)-Al(1) bond lengths are 2.63 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to three equivalent Er(1), three equivalent Er(2), one Fe(1), one Fe(3), two equivalent Fe(2), and two equivalent Al(2) atoms to form distorted AlEr6Al2Fe4 cuboctahedra that share corners with two equivalent Fe(3)Er6Al2Fe4 cuboctahedra, corners with two equivalent Fe(1)Er6Al6 cuboctahedra, corners with four equivalent Fe(2)Er6Al2Fe4 cuboctahedra, corners with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, edges with six equivalent Al(1)Er6Al2Fe4 cuboctahedra, faces with two equivalent Al(1)Er6Al2Fe4 cuboctahedra, faces with three equivalent Fe(3)Er6Al2Fe4 cuboctahedra, faces with three equivalent Fe(1)Er6Al6 cuboctahedra, faces with six equivalent Fe(2)Er6Al2Fe4 cuboctahedra, and faces with six equivalent Al(2)Er6Al4Fe2 cuboctahedra. Both Al(1)-Al(2) bond lengths are 2.79 Å. In the second Al site, Al(2) is bonded to two equivalent Er(2), four equivalent Er(1), two equivalent Fe(1), two equivalent Al(1), and two equivalent Al(2) atoms to form distorted AlEr6Al4Fe2 cuboctahedra that share corners with four equivalent Fe(3)Er6Al2Fe4 cuboctahedra, corners with four equivalent Al(1)Er6Al2Fe4 cuboctahedra, corners with four equivalent Al(2)Er6Al4Fe2 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 Fe(3)Er6Al2Fe4 cuboctahedra, faces with four equivalent Fe(1)Er6Al6 cuboctahedra, faces with four equivalent Al(2)Er6Al4Fe2 cuboctahedra, and faces with six equivalent Al(1)Er6Al2Fe4 cuboctahedra. There is one shorter (2.65 Å) and one longer (2.72 Å) Al(2)-Al(2) bond length.