CsYb3Se4 is MAX Phase structured and crystallizes in the hexagonal P6_3/mmc space group. Cs(1) is bonded in a 6-coordinate geometry to six equivalent Se(1) atoms. There are two inequivalent Yb sites. In the first Yb site, Yb(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form a mixture of corner and edge-sharing YbSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. In the second Yb site, Yb(2) is bonded to six equivalent Se(2) atoms to form a mixture of corner and edge-sharing YbSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Cs(1) and three equivalent Yb(1) atoms to form distorted SeCs3Yb3 octahedra that share corners with three equivalent Se(2)Yb6 octahedra, corners with six equivalent Se(1)Cs3Yb3 octahedra, edges with three equivalent Se(2)Yb6 octahedra, edges with six equivalent Se(1)Cs3Yb3 octahedra, and  a faceface with one Se(1)Cs3Yb3 octahedra. The corner-sharing octahedral tilt angles range from 2-39°. In the second Se site, Se(2) is bonded to three equivalent Yb(1) and three equivalent Yb(2) atoms to form SeYb6 octahedra that share corners with three equivalent Se(1)Cs3Yb3 octahedra, corners with three equivalent Se(2)Yb6 octahedra, edges with three equivalent Se(1)Cs3Yb3 octahedra, and edges with nine equivalent Se(2)Yb6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°.
CsYb3Se4 is MAX Phase structured and crystallizes in the hexagonal P6_3/mmc space group. Cs(1) is bonded in a 6-coordinate geometry to six equivalent Se(1) atoms. All Cs(1)-Se(1) bond lengths are 3.63 Å. There are two inequivalent Yb sites. In the first Yb site, Yb(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form a mixture of corner and edge-sharing YbSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. All Yb(1)-Se(1) bond lengths are 2.92 Å. All Yb(1)-Se(2) bond lengths are 3.00 Å. In the second Yb site, Yb(2) is bonded to six equivalent Se(2) atoms to form a mixture of corner and edge-sharing YbSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. All Yb(2)-Se(2) bond lengths are 2.96 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Cs(1) and three equivalent Yb(1) atoms to form distorted SeCs3Yb3 octahedra that share corners with three equivalent Se(2)Yb6 octahedra, corners with six equivalent Se(1)Cs3Yb3 octahedra, edges with three equivalent Se(2)Yb6 octahedra, edges with six equivalent Se(1)Cs3Yb3 octahedra, and  a faceface with one Se(1)Cs3Yb3 octahedra. The corner-sharing octahedral tilt angles range from 2-39°. In the second Se site, Se(2) is bonded to three equivalent Yb(1) and three equivalent Yb(2) atoms to form SeYb6 octahedra that share corners with three equivalent Se(1)Cs3Yb3 octahedra, corners with three equivalent Se(2)Yb6 octahedra, edges with three equivalent Se(1)Cs3Yb3 octahedra, and edges with nine equivalent Se(2)Yb6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°.