CsCeSiSe4 crystallizes in the orthorhombic P2_12_12_1 space group. Cs(1) is bonded in a 8-coordinate geometry to one Se(3), two equivalent Se(2), two equivalent Se(4), and three equivalent Se(1) atoms. Ce(1) is bonded in a 7-coordinate geometry to one Se(1), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms. Si(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), one Se(3), and one Se(4) atom. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to three equivalent Cs(1), one Ce(1), and one Si(1) atom. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to two equivalent Cs(1), two equivalent Ce(1), and one Si(1) atom. In the third Se site, Se(3) is bonded in a distorted see-saw-like geometry to one Cs(1), two equivalent Ce(1), and one Si(1) atom. In the fourth Se site, Se(4) is bonded in a 5-coordinate geometry to two equivalent Cs(1), two equivalent Ce(1), and one Si(1) atom.
CsCeSiSe4 crystallizes in the orthorhombic P2_12_12_1 space group. Cs(1) is bonded in a 8-coordinate geometry to one Se(3), two equivalent Se(2), two equivalent Se(4), and three equivalent Se(1) atoms. The Cs(1)-Se(3) bond length is 3.62 Å. There is one shorter (3.81 Å) and one longer (4.04 Å) Cs(1)-Se(2) bond length. There is one shorter (3.89 Å) and one longer (3.94 Å) Cs(1)-Se(4) bond length. There are a spread of Cs(1)-Se(1) bond distances ranging from 3.72-3.87 Å. Ce(1) is bonded in a 7-coordinate geometry to one Se(1), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms. The Ce(1)-Se(1) bond length is 3.03 Å. There is one shorter (3.10 Å) and one longer (3.14 Å) Ce(1)-Se(2) bond length. There is one shorter (3.03 Å) and one longer (3.18 Å) Ce(1)-Se(3) bond length. There is one shorter (3.05 Å) and one longer (3.10 Å) Ce(1)-Se(4) bond length. Si(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), one Se(3), and one Se(4) atom. The Si(1)-Se(1) bond length is 2.27 Å. The Si(1)-Se(2) bond length is 2.30 Å. The Si(1)-Se(3) bond length is 2.29 Å. The Si(1)-Se(4) bond length is 2.30 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to three equivalent Cs(1), one Ce(1), and one Si(1) atom. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to two equivalent Cs(1), two equivalent Ce(1), and one Si(1) atom. In the third Se site, Se(3) is bonded in a distorted see-saw-like geometry to one Cs(1), two equivalent Ce(1), and one Si(1) atom. In the fourth Se site, Se(4) is bonded in a 5-coordinate geometry to two equivalent Cs(1), two equivalent Ce(1), and one Si(1) atom.