Tm3Ni8Al crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 12-coordinate geometry to nine equivalent Ni(1) and three equivalent Al(1) atoms. In the second Tm site, Tm(2) is bonded in a distorted hexagonal planar geometry to three equivalent Ni(2), three equivalent Ni(3), and twelve equivalent Ni(1) atoms. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent Tm(2), three equivalent Tm(1), one Ni(2), one Ni(3), four equivalent Ni(1), and one Al(1) atom to form distorted NiTm5AlNi6 cuboctahedra that share corners with two equivalent Al(1)Tm6Ni6 cuboctahedra, corners with fifteen equivalent Ni(1)Tm5AlNi6 cuboctahedra, edges with eight equivalent Ni(1)Tm5AlNi6 cuboctahedra, faces with three equivalent Al(1)Tm6Ni6 cuboctahedra, and faces with eleven equivalent Ni(1)Tm5AlNi6 cuboctahedra. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to three equivalent Tm(2) and six equivalent Ni(1) atoms. In the third Ni site, Ni(3) is bonded in a 9-coordinate geometry to three equivalent Tm(2) and six equivalent Ni(1) atoms. Al(1) is bonded to six equivalent Tm(1) and six equivalent Ni(1) atoms to form distorted AlTm6Ni6 cuboctahedra that share corners with twelve equivalent Ni(1)Tm5AlNi6 cuboctahedra, edges with six equivalent Al(1)Tm6Ni6 cuboctahedra, and faces with eighteen equivalent Ni(1)Tm5AlNi6 cuboctahedra.
Tm3Ni8Al crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 12-coordinate geometry to nine equivalent Ni(1) and three equivalent Al(1) atoms. There are six shorter (2.82 Å) and three longer (3.05 Å) Tm(1)-Ni(1) bond lengths. All Tm(1)-Al(1) bond lengths are 2.99 Å. In the second Tm site, Tm(2) is bonded in a distorted hexagonal planar geometry to three equivalent Ni(2), three equivalent Ni(3), and twelve equivalent Ni(1) atoms. All Tm(2)-Ni(2) bond lengths are 2.90 Å. All Tm(2)-Ni(3) bond lengths are 2.90 Å. All Tm(2)-Ni(1) bond lengths are 3.21 Å. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent Tm(2), three equivalent Tm(1), one Ni(2), one Ni(3), four equivalent Ni(1), and one Al(1) atom to form distorted NiTm5AlNi6 cuboctahedra that share corners with two equivalent Al(1)Tm6Ni6 cuboctahedra, corners with fifteen equivalent Ni(1)Tm5AlNi6 cuboctahedra, edges with eight equivalent Ni(1)Tm5AlNi6 cuboctahedra, faces with three equivalent Al(1)Tm6Ni6 cuboctahedra, and faces with eleven equivalent Ni(1)Tm5AlNi6 cuboctahedra. The Ni(1)-Ni(2) bond length is 2.45 Å. The Ni(1)-Ni(3) bond length is 2.48 Å. There are two shorter (2.47 Å) and two longer (2.55 Å) Ni(1)-Ni(1) bond lengths. The Ni(1)-Al(1) bond length is 2.47 Å. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to three equivalent Tm(2) and six equivalent Ni(1) atoms. In the third Ni site, Ni(3) is bonded in a 9-coordinate geometry to three equivalent Tm(2) and six equivalent Ni(1) atoms. Al(1) is bonded to six equivalent Tm(1) and six equivalent Ni(1) atoms to form distorted AlTm6Ni6 cuboctahedra that share corners with twelve equivalent Ni(1)Tm5AlNi6 cuboctahedra, edges with six equivalent Al(1)Tm6Ni6 cuboctahedra, and faces with eighteen equivalent Ni(1)Tm5AlNi6 cuboctahedra.