KCeSiS4 crystallizes in the monoclinic P2_1/m space group. K(1) is bonded in a 8-coordinate geometry to one S(3), three equivalent S(2), and four equivalent S(1) atoms. Ce(1) is bonded in a 8-coordinate geometry to one S(2), three equivalent S(3), and four equivalent S(1) atoms. Si(1) is bonded in a tetrahedral geometry to one S(2), one S(3), and two equivalent S(1) atoms. There are three inequivalent S sites. In the first S site, S(1) is bonded to two equivalent K(1), two equivalent Ce(1), and one Si(1) atom to form distorted SK2Ce2Si square pyramids that share corners with four equivalent S(1)K2Ce2Si square pyramids, corners with five equivalent S(2)K3CeSi trigonal bipyramids, edges with three equivalent S(1)K2Ce2Si square pyramids, edges with two equivalent S(2)K3CeSi trigonal bipyramids, and  a faceface with one S(1)K2Ce2Si square pyramid. In the second S site, S(2) is bonded to three equivalent K(1), one Ce(1), and one Si(1) atom to form distorted SK3CeSi trigonal bipyramids that share corners with ten equivalent S(1)K2Ce2Si square pyramids, corners with two equivalent S(2)K3CeSi trigonal bipyramids, edges with four equivalent S(1)K2Ce2Si square pyramids, and edges with two equivalent S(2)K3CeSi trigonal bipyramids. In the third S site, S(3) is bonded in a 5-coordinate geometry to one K(1), three equivalent Ce(1), and one Si(1) atom.
KCeSiS4 crystallizes in the monoclinic P2_1/m space group. K(1) is bonded in a 8-coordinate geometry to one S(3), three equivalent S(2), and four equivalent S(1) atoms. The K(1)-S(3) bond length is 3.36 Å. There is one shorter (3.31 Å) and two longer (3.48 Å) K(1)-S(2) bond lengths. There are two shorter (3.37 Å) and two longer (3.49 Å) K(1)-S(1) bond lengths. Ce(1) is bonded in a 8-coordinate geometry to one S(2), three equivalent S(3), and four equivalent S(1) atoms. The Ce(1)-S(2) bond length is 2.86 Å. There is one shorter (2.89 Å) and two longer (3.47 Å) Ce(1)-S(3) bond lengths. There are two shorter (2.94 Å) and two longer (2.96 Å) Ce(1)-S(1) bond lengths. Si(1) is bonded in a tetrahedral geometry to one S(2), one S(3), and two equivalent S(1) atoms. The Si(1)-S(2) bond length is 2.11 Å. The Si(1)-S(3) bond length is 2.14 Å. Both Si(1)-S(1) bond lengths are 2.13 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded to two equivalent K(1), two equivalent Ce(1), and one Si(1) atom to form distorted SK2Ce2Si square pyramids that share corners with four equivalent S(1)K2Ce2Si square pyramids, corners with five equivalent S(2)K3CeSi trigonal bipyramids, edges with three equivalent S(1)K2Ce2Si square pyramids, edges with two equivalent S(2)K3CeSi trigonal bipyramids, and  a faceface with one S(1)K2Ce2Si square pyramid. In the second S site, S(2) is bonded to three equivalent K(1), one Ce(1), and one Si(1) atom to form distorted SK3CeSi trigonal bipyramids that share corners with ten equivalent S(1)K2Ce2Si square pyramids, corners with two equivalent S(2)K3CeSi trigonal bipyramids, edges with four equivalent S(1)K2Ce2Si square pyramids, and edges with two equivalent S(2)K3CeSi trigonal bipyramids. In the third S site, S(3) is bonded in a 5-coordinate geometry to one K(1), three equivalent Ce(1), and one Si(1) atom.