Tm2Co17 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 18-coordinate geometry to six equivalent Co(3) and twelve equivalent Co(4) atoms. In the second Tm site, Tm(2) is bonded in a 20-coordinate geometry to two equivalent Co(1), six equivalent Co(2), six equivalent Co(3), and six equivalent Co(4) atoms. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 14-coordinate geometry to one Tm(2), one Co(1), three equivalent Co(2), three equivalent Co(4), and six equivalent Co(3) atoms. In the second Co site, Co(2) is bonded to two equivalent Tm(2), two equivalent Co(1), four equivalent Co(3), and four equivalent Co(4) atoms to form CoTm2Co10 cuboctahedra that share corners with four equivalent Co(2)Tm2Co10 cuboctahedra, corners with ten equivalent Co(4)Tm3Co9 cuboctahedra, edges with six equivalent Co(4)Tm3Co9 cuboctahedra, faces with four equivalent Co(4)Tm3Co9 cuboctahedra, and faces with six equivalent Co(2)Tm2Co10 cuboctahedra. In the third Co site, Co(3) is bonded in a 12-coordinate geometry to one Tm(1), one Tm(2), two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms. In the fourth Co site, Co(4) is bonded to one Tm(2), two equivalent Tm(1), one Co(1), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(3) atoms to form distorted CoTm3Co9 cuboctahedra that share corners with five equivalent Co(2)Tm2Co10 cuboctahedra, corners with ten equivalent Co(4)Tm3Co9 cuboctahedra, edges with three equivalent Co(2)Tm2Co10 cuboctahedra, edges with five equivalent Co(4)Tm3Co9 cuboctahedra, faces with two equivalent Co(2)Tm2Co10 cuboctahedra, and faces with eight equivalent Co(4)Tm3Co9 cuboctahedra.
Tm2Co17 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 18-coordinate geometry to six equivalent Co(3) and twelve equivalent Co(4) atoms. All Tm(1)-Co(3) bond lengths are 2.88 Å. There are six shorter (2.96 Å) and six longer (3.18 Å) Tm(1)-Co(4) bond lengths. In the second Tm site, Tm(2) is bonded in a 20-coordinate geometry to two equivalent Co(1), six equivalent Co(2), six equivalent Co(3), and six equivalent Co(4) atoms. Both Tm(2)-Co(1) bond lengths are 2.84 Å. All Tm(2)-Co(2) bond lengths are 3.08 Å. All Tm(2)-Co(3) bond lengths are 2.93 Å. All Tm(2)-Co(4) bond lengths are 2.99 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 14-coordinate geometry to one Tm(2), one Co(1), three equivalent Co(2), three equivalent Co(4), and six equivalent Co(3) atoms. The Co(1)-Co(1) bond length is 2.26 Å. All Co(1)-Co(2) bond lengths are 2.51 Å. All Co(1)-Co(4) bond lengths are 2.59 Å. All Co(1)-Co(3) bond lengths are 2.64 Å. In the second Co site, Co(2) is bonded to two equivalent Tm(2), two equivalent Co(1), four equivalent Co(3), and four equivalent Co(4) atoms to form CoTm2Co10 cuboctahedra that share corners with four equivalent Co(2)Tm2Co10 cuboctahedra, corners with ten equivalent Co(4)Tm3Co9 cuboctahedra, edges with six equivalent Co(4)Tm3Co9 cuboctahedra, faces with four equivalent Co(4)Tm3Co9 cuboctahedra, and faces with six equivalent Co(2)Tm2Co10 cuboctahedra. All Co(2)-Co(3) bond lengths are 2.35 Å. All Co(2)-Co(4) bond lengths are 2.37 Å. In the third Co site, Co(3) is bonded in a 12-coordinate geometry to one Tm(1), one Tm(2), two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms. There is one shorter (2.33 Å) and one longer (2.43 Å) Co(3)-Co(3) bond length. There are two shorter (2.47 Å) and two longer (2.48 Å) Co(3)-Co(4) bond lengths. In the fourth Co site, Co(4) is bonded to one Tm(2), two equivalent Tm(1), one Co(1), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(3) atoms to form distorted CoTm3Co9 cuboctahedra that share corners with five equivalent Co(2)Tm2Co10 cuboctahedra, corners with ten equivalent Co(4)Tm3Co9 cuboctahedra, edges with three equivalent Co(2)Tm2Co10 cuboctahedra, edges with five equivalent Co(4)Tm3Co9 cuboctahedra, faces with two equivalent Co(2)Tm2Co10 cuboctahedra, and faces with eight equivalent Co(4)Tm3Co9 cuboctahedra. Both Co(4)-Co(4) bond lengths are 2.36 Å.