Tb5Bi3 crystallizes in the orthorhombic Pnma space group. There are four inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one Bi(1) and four equivalent Bi(2) atoms to form distorted TbBi5 trigonal bipyramids that share corners with six equivalent Tb(4)Bi6 octahedra, corners with four equivalent Tb(3)Bi5 square pyramids, edges with two equivalent Tb(4)Bi6 octahedra,  an edgeedge with one Tb(3)Bi5 square pyramid, edges with two equivalent Tb(1)Bi5 trigonal bipyramids, and  a faceface with one Tb(3)Bi5 square pyramid. The corner-sharing octahedral tilt angles range from 31-41°. In the second Tb site, Tb(2) is bonded in a 5-coordinate geometry to two equivalent Bi(1) and three equivalent Bi(2) atoms. In the third Tb site, Tb(3) is bonded to one Bi(1) and four equivalent Bi(2) atoms to form distorted TbBi5 square pyramids that share corners with five equivalent Tb(4)Bi6 octahedra, corners with four equivalent Tb(1)Bi5 trigonal bipyramids,  an edgeedge with one Tb(4)Bi6 octahedra, edges with two equivalent Tb(3)Bi5 square pyramids,  an edgeedge with one Tb(1)Bi5 trigonal bipyramid,  a faceface with one Tb(4)Bi6 octahedra, and  a faceface with one Tb(1)Bi5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 37-46°. In the fourth Tb site, Tb(4) is bonded to two equivalent Bi(1) and four equivalent Bi(2) atoms to form distorted TbBi6 octahedra that share corners with five equivalent Tb(3)Bi5 square pyramids, corners with six equivalent Tb(1)Bi5 trigonal bipyramids,  an edgeedge with one Tb(3)Bi5 square pyramid, edges with two equivalent Tb(1)Bi5 trigonal bipyramids, faces with two equivalent Tb(4)Bi6 octahedra, and  a faceface with one Tb(3)Bi5 square pyramid. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 8-coordinate geometry to one Tb(1), one Tb(3), two equivalent Tb(4), and four equivalent Tb(2) atoms. In the second Bi site, Bi(2) is bonded in a 9-coordinate geometry to two equivalent Tb(1), two equivalent Tb(3), two equivalent Tb(4), and three equivalent Tb(2) atoms.
Tb5Bi3 crystallizes in the orthorhombic Pnma space group. There are four inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one Bi(1) and four equivalent Bi(2) atoms to form distorted TbBi5 trigonal bipyramids that share corners with six equivalent Tb(4)Bi6 octahedra, corners with four equivalent Tb(3)Bi5 square pyramids, edges with two equivalent Tb(4)Bi6 octahedra,  an edgeedge with one Tb(3)Bi5 square pyramid, edges with two equivalent Tb(1)Bi5 trigonal bipyramids, and  a faceface with one Tb(3)Bi5 square pyramid. The corner-sharing octahedral tilt angles range from 31-41°. The Tb(1)-Bi(1) bond length is 3.13 Å. There are two shorter (3.22 Å) and two longer (3.37 Å) Tb(1)-Bi(2) bond lengths. In the second Tb site, Tb(2) is bonded in a 5-coordinate geometry to two equivalent Bi(1) and three equivalent Bi(2) atoms. There is one shorter (3.10 Å) and one longer (3.19 Å) Tb(2)-Bi(1) bond length. There are a spread of Tb(2)-Bi(2) bond distances ranging from 3.42-3.50 Å. In the third Tb site, Tb(3) is bonded to one Bi(1) and four equivalent Bi(2) atoms to form distorted TbBi5 square pyramids that share corners with five equivalent Tb(4)Bi6 octahedra, corners with four equivalent Tb(1)Bi5 trigonal bipyramids,  an edgeedge with one Tb(4)Bi6 octahedra, edges with two equivalent Tb(3)Bi5 square pyramids,  an edgeedge with one Tb(1)Bi5 trigonal bipyramid,  a faceface with one Tb(4)Bi6 octahedra, and  a faceface with one Tb(1)Bi5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 37-46°. The Tb(3)-Bi(1) bond length is 3.20 Å. There are two shorter (3.20 Å) and two longer (3.26 Å) Tb(3)-Bi(2) bond lengths. In the fourth Tb site, Tb(4) is bonded to two equivalent Bi(1) and four equivalent Bi(2) atoms to form distorted TbBi6 octahedra that share corners with five equivalent Tb(3)Bi5 square pyramids, corners with six equivalent Tb(1)Bi5 trigonal bipyramids,  an edgeedge with one Tb(3)Bi5 square pyramid, edges with two equivalent Tb(1)Bi5 trigonal bipyramids, faces with two equivalent Tb(4)Bi6 octahedra, and  a faceface with one Tb(3)Bi5 square pyramid. There is one shorter (3.13 Å) and one longer (3.44 Å) Tb(4)-Bi(1) bond length. There are two shorter (3.22 Å) and two longer (3.44 Å) Tb(4)-Bi(2) bond lengths. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 8-coordinate geometry to one Tb(1), one Tb(3), two equivalent Tb(4), and four equivalent Tb(2) atoms. In the second Bi site, Bi(2) is bonded in a 9-coordinate geometry to two equivalent Tb(1), two equivalent Tb(3), two equivalent Tb(4), and three equivalent Tb(2) atoms.