Er5Tl3 crystallizes in the tetragonal I4/mcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to two equivalent Tl(1) and four equivalent Tl(2) atoms to form distorted corner-sharing ErTl6 octahedra. The corner-sharing octahedral tilt angles range from 0-49°. In the second Er site, Er(2) is bonded in a 5-coordinate geometry to two equivalent Tl(1) and three equivalent Tl(2) atoms. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a 10-coordinate geometry to two equivalent Er(1) and eight equivalent Er(2) atoms. In the second Tl site, Tl(2) is bonded in a 9-coordinate geometry to two equivalent Er(1), six equivalent Er(2), and one Tl(2) atom.
Er5Tl3 crystallizes in the tetragonal I4/mcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to two equivalent Tl(1) and four equivalent Tl(2) atoms to form distorted corner-sharing ErTl6 octahedra. The corner-sharing octahedral tilt angles range from 0-49°. Both Er(1)-Tl(1) bond lengths are 3.58 Å. All Er(1)-Tl(2) bond lengths are 3.10 Å. In the second Er site, Er(2) is bonded in a 5-coordinate geometry to two equivalent Tl(1) and three equivalent Tl(2) atoms. Both Er(2)-Tl(1) bond lengths are 3.32 Å. There is one shorter (3.17 Å) and two longer (3.22 Å) Er(2)-Tl(2) bond lengths. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a 10-coordinate geometry to two equivalent Er(1) and eight equivalent Er(2) atoms. In the second Tl site, Tl(2) is bonded in a 9-coordinate geometry to two equivalent Er(1), six equivalent Er(2), and one Tl(2) atom. The Tl(2)-Tl(2) bond length is 3.08 Å.