ErGdAl6 crystallizes in the hexagonal P6_3/mmc space group. Er(1) is bonded to six equivalent Al(1) and six equivalent Al(2) atoms to form ErAl12 cuboctahedra that share corners with twelve equivalent Er(1)Al12 cuboctahedra, edges with twelve equivalent Al(2)Gd2Er2Al8 cuboctahedra, faces with six equivalent Gd(1)Al12 cuboctahedra, and faces with six equivalent Al(2)Gd2Er2Al8 cuboctahedra. Gd(1) is bonded to six equivalent Al(1) and six equivalent Al(2) atoms to form GdAl12 cuboctahedra that share corners with six equivalent Gd(1)Al12 cuboctahedra, corners with twelve equivalent Al(2)Gd2Er2Al8 cuboctahedra, edges with six equivalent Al(2)Gd2Er2Al8 cuboctahedra, faces with two equivalent Gd(1)Al12 cuboctahedra, faces with six equivalent Er(1)Al12 cuboctahedra, and faces with six equivalent Al(2)Gd2Er2Al8 cuboctahedra. There are two inequivalent Al sites. In the first Al site, Al(2) is bonded to two equivalent Er(1), two equivalent Gd(1), four equivalent Al(1), and four equivalent Al(2) atoms to form distorted AlGd2Er2Al8 cuboctahedra that share corners with four equivalent Gd(1)Al12 cuboctahedra, corners with fourteen equivalent Al(2)Gd2Er2Al8 cuboctahedra, edges with two equivalent Gd(1)Al12 cuboctahedra, edges with four equivalent Er(1)Al12 cuboctahedra, edges with four equivalent Al(2)Gd2Er2Al8 cuboctahedra, faces with two equivalent Er(1)Al12 cuboctahedra, faces with two equivalent Gd(1)Al12 cuboctahedra, and faces with six equivalent Al(2)Gd2Er2Al8 cuboctahedra. In the second Al site, Al(1) is bonded in a 10-coordinate geometry to two equivalent Er(1), two equivalent Gd(1), two equivalent Al(1), and four equivalent Al(2) atoms.
ErGdAl6 crystallizes in the hexagonal P6_3/mmc space group. Er(1) is bonded to six equivalent Al(1) and six equivalent Al(2) atoms to form ErAl12 cuboctahedra that share corners with twelve equivalent Er(1)Al12 cuboctahedra, edges with twelve equivalent Al(2)Gd2Er2Al8 cuboctahedra, faces with six equivalent Gd(1)Al12 cuboctahedra, and faces with six equivalent Al(2)Gd2Er2Al8 cuboctahedra. All Er(1)-Al(1) bond lengths are 3.05 Å. All Er(1)-Al(2) bond lengths are 2.95 Å. Gd(1) is bonded to six equivalent Al(1) and six equivalent Al(2) atoms to form GdAl12 cuboctahedra that share corners with six equivalent Gd(1)Al12 cuboctahedra, corners with twelve equivalent Al(2)Gd2Er2Al8 cuboctahedra, edges with six equivalent Al(2)Gd2Er2Al8 cuboctahedra, faces with two equivalent Gd(1)Al12 cuboctahedra, faces with six equivalent Er(1)Al12 cuboctahedra, and faces with six equivalent Al(2)Gd2Er2Al8 cuboctahedra. All Gd(1)-Al(1) bond lengths are 3.06 Å. All Gd(1)-Al(2) bond lengths are 3.04 Å. There are two inequivalent Al sites. In the first Al site, Al(2) is bonded to two equivalent Er(1), two equivalent Gd(1), four equivalent Al(1), and four equivalent Al(2) atoms to form distorted AlGd2Er2Al8 cuboctahedra that share corners with four equivalent Gd(1)Al12 cuboctahedra, corners with fourteen equivalent Al(2)Gd2Er2Al8 cuboctahedra, edges with two equivalent Gd(1)Al12 cuboctahedra, edges with four equivalent Er(1)Al12 cuboctahedra, edges with four equivalent Al(2)Gd2Er2Al8 cuboctahedra, faces with two equivalent Er(1)Al12 cuboctahedra, faces with two equivalent Gd(1)Al12 cuboctahedra, and faces with six equivalent Al(2)Gd2Er2Al8 cuboctahedra. All Al(2)-Al(1) bond lengths are 2.90 Å. All Al(2)-Al(2) bond lengths are 3.04 Å. In the second Al site, Al(1) is bonded in a 10-coordinate geometry to two equivalent Er(1), two equivalent Gd(1), two equivalent Al(1), and four equivalent Al(2) atoms. Both Al(1)-Al(1) bond lengths are 2.74 Å.