Tm5Sb3 crystallizes in the orthorhombic Pnma space group. There are four inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 5-coordinate geometry to two equivalent Sb(2) and three equivalent Sb(1) atoms. In the second Tm site, Tm(2) is bonded to one Sb(2) and four equivalent Sb(1) atoms to form distorted edge-sharing TmSb5 square pyramids. In the third Tm site, Tm(3) is bonded in a 6-coordinate geometry to two equivalent Sb(2) and four equivalent Sb(1) atoms. In the fourth Tm site, Tm(4) is bonded in a 5-coordinate geometry to one Sb(2) and four equivalent Sb(1) atoms. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded in a 9-coordinate geometry to two equivalent Tm(2), two equivalent Tm(3), two equivalent Tm(4), and three equivalent Tm(1) atoms. In the second Sb site, Sb(2) is bonded in a 8-coordinate geometry to one Tm(2), one Tm(4), two equivalent Tm(3), and four equivalent Tm(1) atoms.
Tm5Sb3 crystallizes in the orthorhombic Pnma space group. There are four inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 5-coordinate geometry to two equivalent Sb(2) and three equivalent Sb(1) atoms. There is one shorter (2.97 Å) and one longer (3.07 Å) Tm(1)-Sb(2) bond length. There are a spread of Tm(1)-Sb(1) bond distances ranging from 3.23-3.47 Å. In the second Tm site, Tm(2) is bonded to one Sb(2) and four equivalent Sb(1) atoms to form distorted edge-sharing TmSb5 square pyramids. The Tm(2)-Sb(2) bond length is 3.06 Å. There are two shorter (3.10 Å) and two longer (3.12 Å) Tm(2)-Sb(1) bond lengths. In the third Tm site, Tm(3) is bonded in a 6-coordinate geometry to two equivalent Sb(2) and four equivalent Sb(1) atoms. There is one shorter (3.00 Å) and one longer (3.45 Å) Tm(3)-Sb(2) bond length. There are two shorter (3.12 Å) and two longer (3.24 Å) Tm(3)-Sb(1) bond lengths. In the fourth Tm site, Tm(4) is bonded in a 5-coordinate geometry to one Sb(2) and four equivalent Sb(1) atoms. The Tm(4)-Sb(2) bond length is 2.96 Å. There are two shorter (3.17 Å) and two longer (3.25 Å) Tm(4)-Sb(1) bond lengths. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded in a 9-coordinate geometry to two equivalent Tm(2), two equivalent Tm(3), two equivalent Tm(4), and three equivalent Tm(1) atoms. In the second Sb site, Sb(2) is bonded in a 8-coordinate geometry to one Tm(2), one Tm(4), two equivalent Tm(3), and four equivalent Tm(1) atoms.