Sm2HfS5 crystallizes in the orthorhombic Pnma space group. Sm(1) is bonded in a 8-coordinate geometry to two equivalent S(1), two equivalent S(2), two equivalent S(3), and two equivalent S(4) atoms. Hf(1) is bonded to one S(2), one S(3), one S(4), and four equivalent S(1) atoms to form distorted edge-sharing HfS7 pentagonal bipyramids. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Sm(1) and two equivalent Hf(1) atoms to form distorted SSm2Hf2 trigonal pyramids that share corners with four equivalent S(3)Sm4Hf square pyramids, corners with two equivalent S(2)Sm4Hf trigonal bipyramids, corners with two equivalent S(4)Sm4Hf trigonal bipyramids, corners with six equivalent S(1)Sm2Hf2 trigonal pyramids,  an edgeedge with one S(3)Sm4Hf square pyramid, edges with two equivalent S(2)Sm4Hf trigonal bipyramids, edges with two equivalent S(4)Sm4Hf trigonal bipyramids, and  an edgeedge with one S(1)Sm2Hf2 trigonal pyramid. In the second S site, S(2) is bonded to four equivalent Sm(1) and one Hf(1) atom to form distorted SSm4Hf trigonal bipyramids that share corners with five equivalent S(3)Sm4Hf square pyramids,  a cornercorner with one S(4)Sm4Hf trigonal bipyramid, corners with four equivalent S(2)Sm4Hf trigonal bipyramids, corners with four equivalent S(1)Sm2Hf2 trigonal pyramids, edges with two equivalent S(3)Sm4Hf square pyramids, edges with four equivalent S(4)Sm4Hf trigonal bipyramids, and edges with four equivalent S(1)Sm2Hf2 trigonal pyramids. In the third S site, S(3) is bonded to four equivalent Sm(1) and one Hf(1) atom to form SSm4Hf square pyramids that share corners with four equivalent S(4)Sm4Hf trigonal bipyramids, corners with five equivalent S(2)Sm4Hf trigonal bipyramids, corners with eight equivalent S(1)Sm2Hf2 trigonal pyramids, edges with two equivalent S(3)Sm4Hf square pyramids,  an edgeedge with one S(4)Sm4Hf trigonal bipyramid, edges with two equivalent S(2)Sm4Hf trigonal bipyramids, edges with two equivalent S(1)Sm2Hf2 trigonal pyramids, and  a faceface with one S(4)Sm4Hf trigonal bipyramid. In the fourth S site, S(4) is bonded to four equivalent Sm(1) and one Hf(1) atom to form distorted SSm4Hf trigonal bipyramids that share corners with four equivalent S(3)Sm4Hf square pyramids,  a cornercorner with one S(2)Sm4Hf trigonal bipyramid, corners with four equivalent S(4)Sm4Hf trigonal bipyramids, corners with four equivalent S(1)Sm2Hf2 trigonal pyramids,  an edgeedge with one S(3)Sm4Hf square pyramid, edges with four equivalent S(2)Sm4Hf trigonal bipyramids, edges with four equivalent S(1)Sm2Hf2 trigonal pyramids, and  a faceface with one S(3)Sm4Hf square pyramid.
Sm2HfS5 crystallizes in the orthorhombic Pnma space group. Sm(1) is bonded in a 8-coordinate geometry to two equivalent S(1), two equivalent S(2), two equivalent S(3), and two equivalent S(4) atoms. There is one shorter (2.90 Å) and one longer (2.91 Å) Sm(1)-S(1) bond length. There is one shorter (2.90 Å) and one longer (3.02 Å) Sm(1)-S(2) bond length. Both Sm(1)-S(3) bond lengths are 2.88 Å. There is one shorter (2.86 Å) and one longer (2.90 Å) Sm(1)-S(4) bond length. Hf(1) is bonded to one S(2), one S(3), one S(4), and four equivalent S(1) atoms to form distorted edge-sharing HfS7 pentagonal bipyramids. The Hf(1)-S(2) bond length is 2.65 Å. The Hf(1)-S(3) bond length is 2.71 Å. The Hf(1)-S(4) bond length is 2.58 Å. There are two shorter (2.52 Å) and two longer (2.66 Å) Hf(1)-S(1) bond lengths. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Sm(1) and two equivalent Hf(1) atoms to form distorted SSm2Hf2 trigonal pyramids that share corners with four equivalent S(3)Sm4Hf square pyramids, corners with two equivalent S(2)Sm4Hf trigonal bipyramids, corners with two equivalent S(4)Sm4Hf trigonal bipyramids, corners with six equivalent S(1)Sm2Hf2 trigonal pyramids,  an edgeedge with one S(3)Sm4Hf square pyramid, edges with two equivalent S(2)Sm4Hf trigonal bipyramids, edges with two equivalent S(4)Sm4Hf trigonal bipyramids, and  an edgeedge with one S(1)Sm2Hf2 trigonal pyramid. In the second S site, S(2) is bonded to four equivalent Sm(1) and one Hf(1) atom to form distorted SSm4Hf trigonal bipyramids that share corners with five equivalent S(3)Sm4Hf square pyramids,  a cornercorner with one S(4)Sm4Hf trigonal bipyramid, corners with four equivalent S(2)Sm4Hf trigonal bipyramids, corners with four equivalent S(1)Sm2Hf2 trigonal pyramids, edges with two equivalent S(3)Sm4Hf square pyramids, edges with four equivalent S(4)Sm4Hf trigonal bipyramids, and edges with four equivalent S(1)Sm2Hf2 trigonal pyramids. In the third S site, S(3) is bonded to four equivalent Sm(1) and one Hf(1) atom to form SSm4Hf square pyramids that share corners with four equivalent S(4)Sm4Hf trigonal bipyramids, corners with five equivalent S(2)Sm4Hf trigonal bipyramids, corners with eight equivalent S(1)Sm2Hf2 trigonal pyramids, edges with two equivalent S(3)Sm4Hf square pyramids,  an edgeedge with one S(4)Sm4Hf trigonal bipyramid, edges with two equivalent S(2)Sm4Hf trigonal bipyramids, edges with two equivalent S(1)Sm2Hf2 trigonal pyramids, and  a faceface with one S(4)Sm4Hf trigonal bipyramid. In the fourth S site, S(4) is bonded to four equivalent Sm(1) and one Hf(1) atom to form distorted SSm4Hf trigonal bipyramids that share corners with four equivalent S(3)Sm4Hf square pyramids,  a cornercorner with one S(2)Sm4Hf trigonal bipyramid, corners with four equivalent S(4)Sm4Hf trigonal bipyramids, corners with four equivalent S(1)Sm2Hf2 trigonal pyramids,  an edgeedge with one S(3)Sm4Hf square pyramid, edges with four equivalent S(2)Sm4Hf trigonal bipyramids, edges with four equivalent S(1)Sm2Hf2 trigonal pyramids, and  a faceface with one S(3)Sm4Hf square pyramid.