Tm3(Co2Sn)4 is Hexagonal Laves-derived structured and crystallizes in the hexagonal P6_3mc space group. Tm(1) is bonded in a 12-coordinate geometry to two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), two equivalent Sn(1), and four equivalent Sn(2) atoms. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 10-coordinate geometry to six equivalent Tm(1), one Sn(1), and three equivalent Sn(2) atoms. In the second Co site, Co(2) is bonded to two equivalent Tm(1), two equivalent Co(2), two equivalent Co(4), three equivalent Co(3), and three equivalent Sn(2) atoms to form distorted CoTm2Co7Sn3 cuboctahedra that share corners with four equivalent Co(2)Tm2Co7Sn3 cuboctahedra, corners with five equivalent Sn(2)Tm4Co8 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Tm2Co7Sn3 cuboctahedra, and faces with six equivalent Sn(2)Tm4Co8 cuboctahedra. In the third Co site, Co(3) is bonded in a 10-coordinate geometry to two equivalent Tm(1), one Co(4), three equivalent Co(2), one Sn(1), and three equivalent Sn(2) atoms. In the fourth Co site, Co(4) is bonded to three equivalent Co(3), six equivalent Co(2), and three equivalent Sn(2) atoms to form CoCo9Sn3 cuboctahedra that share corners with three equivalent Sn(2)Tm4Co8 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Tm2Co7Sn3 cuboctahedra, and faces with six equivalent Sn(2)Tm4Co8 cuboctahedra. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 10-coordinate geometry to six equivalent Tm(1), one Co(1), and three equivalent Co(3) atoms. In the second Sn site, Sn(2) is bonded to four equivalent Tm(1), one Co(1), one Co(4), three equivalent Co(2), and three equivalent Co(3) atoms to form distorted SnTm4Co8 cuboctahedra that share  a cornercorner with one Co(4)Co9Sn3 cuboctahedra, corners with four equivalent Sn(2)Tm4Co8 cuboctahedra, corners with five equivalent Co(2)Tm2Co7Sn3 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Tm2Co7Sn3 cuboctahedra, and faces with eight equivalent Sn(2)Tm4Co8 cuboctahedra.
Tm3(Co2Sn)4 is Hexagonal Laves-derived structured and crystallizes in the hexagonal P6_3mc space group. Tm(1) is bonded in a 12-coordinate geometry to two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), two equivalent Sn(1), and four equivalent Sn(2) atoms. There is one shorter (3.13 Å) and one longer (3.37 Å) Tm(1)-Co(1) bond length. Both Tm(1)-Co(2) bond lengths are 3.10 Å. Both Tm(1)-Co(3) bond lengths are 3.01 Å. There is one shorter (3.15 Å) and one longer (3.26 Å) Tm(1)-Sn(1) bond length. There are two shorter (3.15 Å) and two longer (3.17 Å) Tm(1)-Sn(2) bond lengths. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 10-coordinate geometry to six equivalent Tm(1), one Sn(1), and three equivalent Sn(2) atoms. The Co(1)-Sn(1) bond length is 2.63 Å. All Co(1)-Sn(2) bond lengths are 2.50 Å. In the second Co site, Co(2) is bonded to two equivalent Tm(1), two equivalent Co(2), two equivalent Co(4), three equivalent Co(3), and three equivalent Sn(2) atoms to form distorted CoTm2Co7Sn3 cuboctahedra that share corners with four equivalent Co(2)Tm2Co7Sn3 cuboctahedra, corners with five equivalent Sn(2)Tm4Co8 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Tm2Co7Sn3 cuboctahedra, and faces with six equivalent Sn(2)Tm4Co8 cuboctahedra. Both Co(2)-Co(2) bond lengths are 2.63 Å. There is one shorter (2.37 Å) and one longer (2.46 Å) Co(2)-Co(4) bond length. There is one shorter (2.54 Å) and two longer (2.56 Å) Co(2)-Co(3) bond lengths. There is one shorter (2.62 Å) and two longer (2.65 Å) Co(2)-Sn(2) bond lengths. In the third Co site, Co(3) is bonded in a 10-coordinate geometry to two equivalent Tm(1), one Co(4), three equivalent Co(2), one Sn(1), and three equivalent Sn(2) atoms. The Co(3)-Co(4) bond length is 2.48 Å. The Co(3)-Sn(1) bond length is 2.63 Å. There are two shorter (2.72 Å) and one longer (2.77 Å) Co(3)-Sn(2) bond length. In the fourth Co site, Co(4) is bonded to three equivalent Co(3), six equivalent Co(2), and three equivalent Sn(2) atoms to form CoCo9Sn3 cuboctahedra that share corners with three equivalent Sn(2)Tm4Co8 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Tm2Co7Sn3 cuboctahedra, and faces with six equivalent Sn(2)Tm4Co8 cuboctahedra. All Co(4)-Sn(2) bond lengths are 2.66 Å. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 10-coordinate geometry to six equivalent Tm(1), one Co(1), and three equivalent Co(3) atoms. In the second Sn site, Sn(2) is bonded to four equivalent Tm(1), one Co(1), one Co(4), three equivalent Co(2), and three equivalent Co(3) atoms to form distorted SnTm4Co8 cuboctahedra that share  a cornercorner with one Co(4)Co9Sn3 cuboctahedra, corners with four equivalent Sn(2)Tm4Co8 cuboctahedra, corners with five equivalent Co(2)Tm2Co7Sn3 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Tm2Co7Sn3 cuboctahedra, and faces with eight equivalent Sn(2)Tm4Co8 cuboctahedra.