YbTlSe2 is Caswellsilverite structured and crystallizes in the trigonal R-3m space group. Yb(1) is bonded to six equivalent Se(1) atoms to form YbSe6 octahedra that share corners with six equivalent Tl(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Tl(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 4°. Tl(1) is bonded to six equivalent Se(1) atoms to form TlSe6 octahedra that share corners with six equivalent Yb(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Tl(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 4°. Se(1) is bonded to three equivalent Yb(1) and three equivalent Tl(1) atoms to form a mixture of corner and edge-sharing SeYb3Tl3 octahedra. The corner-sharing octahedra are not tilted.
YbTlSe2 is Caswellsilverite structured and crystallizes in the trigonal R-3m space group. Yb(1) is bonded to six equivalent Se(1) atoms to form YbSe6 octahedra that share corners with six equivalent Tl(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Tl(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 4°. All Yb(1)-Se(1) bond lengths are 2.96 Å. Tl(1) is bonded to six equivalent Se(1) atoms to form TlSe6 octahedra that share corners with six equivalent Yb(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Tl(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 4°. All Tl(1)-Se(1) bond lengths are 3.12 Å. Se(1) is bonded to three equivalent Yb(1) and three equivalent Tl(1) atoms to form a mixture of corner and edge-sharing SeYb3Tl3 octahedra. The corner-sharing octahedra are not tilted.