Ce2SiS5 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a 9-coordinate geometry to one S(3), two equivalent S(1), two equivalent S(2), two equivalent S(4), and two equivalent S(5) atoms. In the second Ce site, Ce(2) is bonded in a 8-coordinate geometry to one S(2), one S(5), two equivalent S(1), two equivalent S(3), and two equivalent S(4) atoms. Si(1) is bonded in a tetrahedral geometry to one S(1), one S(2), one S(3), and one S(5) atom. There are five inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Ce(1), two equivalent Ce(2), and one Si(1) atom to form distorted SCe4Si trigonal bipyramids that share corners with five equivalent S(3)Ce3Si tetrahedra, corners with three equivalent S(4)Ce4 trigonal pyramids,  an edgeedge with one S(3)Ce3Si tetrahedra, edges with two equivalent S(1)Ce4Si trigonal bipyramids,  an edgeedge with one S(4)Ce4 trigonal pyramid, and  a faceface with one S(4)Ce4 trigonal pyramid. In the second S site, S(2) is bonded in a distorted rectangular see-saw-like geometry to one Ce(2), two equivalent Ce(1), and one Si(1) atom. In the third S site, S(3) is bonded to one Ce(1), two equivalent Ce(2), and one Si(1) atom to form distorted SCe3Si tetrahedra that share corners with five equivalent S(1)Ce4Si trigonal bipyramids, corners with four equivalent S(4)Ce4 trigonal pyramids,  an edgeedge with one S(3)Ce3Si tetrahedra,  an edgeedge with one S(1)Ce4Si trigonal bipyramid, and  an edgeedge with one S(4)Ce4 trigonal pyramid. In the fourth S site, S(4) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form SCe4 trigonal pyramids that share corners with four equivalent S(3)Ce3Si tetrahedra, corners with three equivalent S(1)Ce4Si trigonal bipyramids, corners with two equivalent S(4)Ce4 trigonal pyramids,  an edgeedge with one S(3)Ce3Si tetrahedra,  an edgeedge with one S(1)Ce4Si trigonal bipyramid,  an edgeedge with one S(4)Ce4 trigonal pyramid, and  a faceface with one S(1)Ce4Si trigonal bipyramid. In the fifth S site, S(5) is bonded in a 4-coordinate geometry to one Ce(2), two equivalent Ce(1), and one Si(1) atom.
Ce2SiS5 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a 9-coordinate geometry to one S(3), two equivalent S(1), two equivalent S(2), two equivalent S(4), and two equivalent S(5) atoms. The Ce(1)-S(3) bond length is 2.92 Å. There is one shorter (3.07 Å) and one longer (3.18 Å) Ce(1)-S(1) bond length. There is one shorter (3.04 Å) and one longer (3.18 Å) Ce(1)-S(2) bond length. There is one shorter (2.88 Å) and one longer (2.96 Å) Ce(1)-S(4) bond length. There is one shorter (3.11 Å) and one longer (3.29 Å) Ce(1)-S(5) bond length. In the second Ce site, Ce(2) is bonded in a 8-coordinate geometry to one S(2), one S(5), two equivalent S(1), two equivalent S(3), and two equivalent S(4) atoms. The Ce(2)-S(2) bond length is 2.93 Å. The Ce(2)-S(5) bond length is 3.09 Å. There is one shorter (2.98 Å) and one longer (3.03 Å) Ce(2)-S(1) bond length. There is one shorter (2.91 Å) and one longer (2.95 Å) Ce(2)-S(3) bond length. Both Ce(2)-S(4) bond lengths are 2.79 Å. Si(1) is bonded in a tetrahedral geometry to one S(1), one S(2), one S(3), and one S(5) atom. The Si(1)-S(1) bond length is 2.16 Å. The Si(1)-S(2) bond length is 2.13 Å. The Si(1)-S(3) bond length is 2.12 Å. The Si(1)-S(5) bond length is 2.12 Å. There are five inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Ce(1), two equivalent Ce(2), and one Si(1) atom to form distorted SCe4Si trigonal bipyramids that share corners with five equivalent S(3)Ce3Si tetrahedra, corners with three equivalent S(4)Ce4 trigonal pyramids,  an edgeedge with one S(3)Ce3Si tetrahedra, edges with two equivalent S(1)Ce4Si trigonal bipyramids,  an edgeedge with one S(4)Ce4 trigonal pyramid, and  a faceface with one S(4)Ce4 trigonal pyramid. In the second S site, S(2) is bonded in a distorted rectangular see-saw-like geometry to one Ce(2), two equivalent Ce(1), and one Si(1) atom. In the third S site, S(3) is bonded to one Ce(1), two equivalent Ce(2), and one Si(1) atom to form distorted SCe3Si tetrahedra that share corners with five equivalent S(1)Ce4Si trigonal bipyramids, corners with four equivalent S(4)Ce4 trigonal pyramids,  an edgeedge with one S(3)Ce3Si tetrahedra,  an edgeedge with one S(1)Ce4Si trigonal bipyramid, and  an edgeedge with one S(4)Ce4 trigonal pyramid. In the fourth S site, S(4) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form SCe4 trigonal pyramids that share corners with four equivalent S(3)Ce3Si tetrahedra, corners with three equivalent S(1)Ce4Si trigonal bipyramids, corners with two equivalent S(4)Ce4 trigonal pyramids,  an edgeedge with one S(3)Ce3Si tetrahedra,  an edgeedge with one S(1)Ce4Si trigonal bipyramid,  an edgeedge with one S(4)Ce4 trigonal pyramid, and  a faceface with one S(1)Ce4Si trigonal bipyramid. In the fifth S site, S(5) is bonded in a 4-coordinate geometry to one Ce(2), two equivalent Ce(1), and one Si(1) atom.