Tm2CoGa8 crystallizes in the tetragonal P4/mmm space group. Tm(1) is bonded to four equivalent Ga(1); four equivalent Ga(2); and four Ga(3,3) atoms to form TmGa12 cuboctahedra that share corners with eight equivalent Tm(1)Ga12 cuboctahedra, edges with four equivalent Ga(2)Tm4Ga8 cuboctahedra, edges with eight equivalent Ga(1)Tm4Ga8 cuboctahedra, faces with four equivalent Ga(1)Tm4Ga8 cuboctahedra, faces with four equivalent Ga(2)Tm4Ga8 cuboctahedra, and faces with five equivalent Tm(1)Ga12 cuboctahedra. Co(1) is bonded in a body-centered cubic geometry to eight Ga(3,3) atoms. There are four inequivalent Ga sites. In the first Ga site, Ga(1) is bonded to four equivalent Tm(1), four equivalent Ga(1), and four equivalent Ga(2) atoms to form distorted GaTm4Ga8 cuboctahedra that share corners with four equivalent Ga(1)Tm4Ga8 cuboctahedra, edges with eight equivalent Tm(1)Ga12 cuboctahedra, edges with eight equivalent Ga(2)Tm4Ga8 cuboctahedra, faces with four equivalent Tm(1)Ga12 cuboctahedra, faces with four equivalent Ga(2)Tm4Ga8 cuboctahedra, and faces with eight equivalent Ga(1)Tm4Ga8 cuboctahedra. In the second Ga site, Ga(2) is bonded to four equivalent Tm(1); four equivalent Ga(1); and four Ga(3,3) atoms to form distorted GaTm4Ga8 cuboctahedra that share corners with eight equivalent Ga(2)Tm4Ga8 cuboctahedra, edges with four equivalent Tm(1)Ga12 cuboctahedra, edges with eight equivalent Ga(1)Tm4Ga8 cuboctahedra, faces with four equivalent Tm(1)Ga12 cuboctahedra, faces with four equivalent Ga(1)Tm4Ga8 cuboctahedra, and faces with five equivalent Ga(2)Tm4Ga8 cuboctahedra. In the third Ga site, Ga(3) is bonded in a 11-coordinate geometry to two equivalent Tm(1); two equivalent Co(1); two equivalent Ga(2); and five Ga(3,3) atoms. In the fourth Ga site, Ga(3) is bonded in a 11-coordinate geometry to two equivalent Tm(1); two equivalent Co(1); two equivalent Ga(2); and five Ga(3,3) atoms.
Tm2CoGa8 crystallizes in the tetragonal P4/mmm space group. Tm(1) is bonded to four equivalent Ga(1); four equivalent Ga(2); and four Ga(3,3) atoms to form TmGa12 cuboctahedra that share corners with eight equivalent Tm(1)Ga12 cuboctahedra, edges with four equivalent Ga(2)Tm4Ga8 cuboctahedra, edges with eight equivalent Ga(1)Tm4Ga8 cuboctahedra, faces with four equivalent Ga(1)Tm4Ga8 cuboctahedra, faces with four equivalent Ga(2)Tm4Ga8 cuboctahedra, and faces with five equivalent Tm(1)Ga12 cuboctahedra. All Tm(1)-Ga(1) bond lengths are 2.97 Å. All Tm(1)-Ga(2) bond lengths are 2.94 Å. All Tm(1)-Ga(3,3) bond lengths are 2.94 Å. Co(1) is bonded in a body-centered cubic geometry to eight Ga(3,3) atoms. All Co(1)-Ga(3,3) bond lengths are 2.44 Å. There are four inequivalent Ga sites. In the first Ga site, Ga(1) is bonded to four equivalent Tm(1), four equivalent Ga(1), and four equivalent Ga(2) atoms to form distorted GaTm4Ga8 cuboctahedra that share corners with four equivalent Ga(1)Tm4Ga8 cuboctahedra, edges with eight equivalent Tm(1)Ga12 cuboctahedra, edges with eight equivalent Ga(2)Tm4Ga8 cuboctahedra, faces with four equivalent Tm(1)Ga12 cuboctahedra, faces with four equivalent Ga(2)Tm4Ga8 cuboctahedra, and faces with eight equivalent Ga(1)Tm4Ga8 cuboctahedra. All Ga(1)-Ga(1) bond lengths are 2.94 Å. All Ga(1)-Ga(2) bond lengths are 2.98 Å. In the second Ga site, Ga(2) is bonded to four equivalent Tm(1); four equivalent Ga(1); and four Ga(3,3) atoms to form distorted GaTm4Ga8 cuboctahedra that share corners with eight equivalent Ga(2)Tm4Ga8 cuboctahedra, edges with four equivalent Tm(1)Ga12 cuboctahedra, edges with eight equivalent Ga(1)Tm4Ga8 cuboctahedra, faces with four equivalent Tm(1)Ga12 cuboctahedra, faces with four equivalent Ga(1)Tm4Ga8 cuboctahedra, and faces with five equivalent Ga(2)Tm4Ga8 cuboctahedra. All Ga(2)-Ga(3,3) bond lengths are 2.93 Å. In the third Ga site, Ga(3) is bonded in a 11-coordinate geometry to two equivalent Tm(1); two equivalent Co(1); two equivalent Ga(2); and five Ga(3,3) atoms. There is one shorter (2.55 Å) and four longer (2.94 Å) Ga(3)-Ga(3,3) bond lengths. In the fourth Ga site, Ga(3) is bonded in a 11-coordinate geometry to two equivalent Tm(1); two equivalent Co(1); two equivalent Ga(2); and five Ga(3,3) atoms. The Ga(3)-Ga(3) bond length is 2.55 Å.