Tm5Bi3 crystallizes in the orthorhombic Pnma space group. There are four inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to one Bi(1) and four equivalent Bi(2) atoms to form distorted TmBi5 square pyramids that share corners with five equivalent Tm(3)Bi6 octahedra,  an edgeedge with one Tm(3)Bi6 octahedra, edges with two equivalent Tm(1)Bi5 square pyramids, and  a faceface with one Tm(3)Bi6 octahedra. The corner-sharing octahedral tilt angles range from 36-46°. In the second Tm site, Tm(2) is bonded in a 5-coordinate geometry to one Bi(1) and four equivalent Bi(2) atoms. In the third Tm site, Tm(3) is bonded to two equivalent Bi(1) and four equivalent Bi(2) atoms to form distorted TmBi6 octahedra that share corners with five equivalent Tm(1)Bi5 square pyramids,  an edgeedge with one Tm(1)Bi5 square pyramid, faces with two equivalent Tm(3)Bi6 octahedra, and  a faceface with one Tm(1)Bi5 square pyramid. In the fourth Tm site, Tm(4) is bonded in a 5-coordinate geometry to two equivalent Bi(1) and three equivalent Bi(2) atoms. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 8-coordinate geometry to one Tm(1), one Tm(2), two equivalent Tm(3), and four equivalent Tm(4) atoms. In the second Bi site, Bi(2) is bonded in a 9-coordinate geometry to two equivalent Tm(1), two equivalent Tm(2), two equivalent Tm(3), and three equivalent Tm(4) atoms.
Tm5Bi3 crystallizes in the orthorhombic Pnma space group. There are four inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to one Bi(1) and four equivalent Bi(2) atoms to form distorted TmBi5 square pyramids that share corners with five equivalent Tm(3)Bi6 octahedra,  an edgeedge with one Tm(3)Bi6 octahedra, edges with two equivalent Tm(1)Bi5 square pyramids, and  a faceface with one Tm(3)Bi6 octahedra. The corner-sharing octahedral tilt angles range from 36-46°. The Tm(1)-Bi(1) bond length is 3.12 Å. There are two shorter (3.15 Å) and two longer (3.20 Å) Tm(1)-Bi(2) bond lengths. In the second Tm site, Tm(2) is bonded in a 5-coordinate geometry to one Bi(1) and four equivalent Bi(2) atoms. The Tm(2)-Bi(1) bond length is 3.08 Å. There are two shorter (3.15 Å) and two longer (3.33 Å) Tm(2)-Bi(2) bond lengths. In the third Tm site, Tm(3) is bonded to two equivalent Bi(1) and four equivalent Bi(2) atoms to form distorted TmBi6 octahedra that share corners with five equivalent Tm(1)Bi5 square pyramids,  an edgeedge with one Tm(1)Bi5 square pyramid, faces with two equivalent Tm(3)Bi6 octahedra, and  a faceface with one Tm(1)Bi5 square pyramid. There is one shorter (3.08 Å) and one longer (3.37 Å) Tm(3)-Bi(1) bond length. There are two shorter (3.15 Å) and two longer (3.39 Å) Tm(3)-Bi(2) bond lengths. In the fourth Tm site, Tm(4) is bonded in a 5-coordinate geometry to two equivalent Bi(1) and three equivalent Bi(2) atoms. There is one shorter (3.07 Å) and one longer (3.14 Å) Tm(4)-Bi(1) bond length. There are two shorter (3.37 Å) and one longer (3.45 Å) Tm(4)-Bi(2) bond length. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 8-coordinate geometry to one Tm(1), one Tm(2), two equivalent Tm(3), and four equivalent Tm(4) atoms. In the second Bi site, Bi(2) is bonded in a 9-coordinate geometry to two equivalent Tm(1), two equivalent Tm(2), two equivalent Tm(3), and three equivalent Tm(4) atoms.