Er3Tl5 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 9-coordinate geometry to one Tl(1), four equivalent Tl(2), and four equivalent Tl(3) atoms. In the second Er site, Er(2) is bonded in a 10-coordinate geometry to two equivalent Tl(1), four equivalent Tl(2), and four equivalent Tl(3) atoms. There are three inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a 11-coordinate geometry to one Er(1), four equivalent Er(2), two equivalent Tl(2), and four equivalent Tl(3) atoms. In the second Tl site, Tl(2) is bonded in a 10-coordinate geometry to two equivalent Er(1), four equivalent Er(2), one Tl(1), one Tl(2), and two equivalent Tl(3) atoms. In the third Tl site, Tl(3) is bonded in a 10-coordinate geometry to two equivalent Er(1), four equivalent Er(2), two equivalent Tl(1), and two equivalent Tl(2) atoms.
Er3Tl5 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 9-coordinate geometry to one Tl(1), four equivalent Tl(2), and four equivalent Tl(3) atoms. The Er(1)-Tl(1) bond length is 3.05 Å. There are two shorter (3.17 Å) and two longer (3.32 Å) Er(1)-Tl(2) bond lengths. There are two shorter (3.11 Å) and two longer (3.49 Å) Er(1)-Tl(3) bond lengths. In the second Er site, Er(2) is bonded in a 10-coordinate geometry to two equivalent Tl(1), four equivalent Tl(2), and four equivalent Tl(3) atoms. Both Er(2)-Tl(1) bond lengths are 3.38 Å. There are two shorter (3.22 Å) and two longer (3.44 Å) Er(2)-Tl(2) bond lengths. There are two shorter (3.21 Å) and two longer (3.51 Å) Er(2)-Tl(3) bond lengths. There are three inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a 11-coordinate geometry to one Er(1), four equivalent Er(2), two equivalent Tl(2), and four equivalent Tl(3) atoms. Both Tl(1)-Tl(2) bond lengths are 3.23 Å. There are two shorter (3.26 Å) and two longer (3.27 Å) Tl(1)-Tl(3) bond lengths. In the second Tl site, Tl(2) is bonded in a 10-coordinate geometry to two equivalent Er(1), four equivalent Er(2), one Tl(1), one Tl(2), and two equivalent Tl(3) atoms. The Tl(2)-Tl(2) bond length is 3.27 Å. Both Tl(2)-Tl(3) bond lengths are 3.20 Å. In the third Tl site, Tl(3) is bonded in a 10-coordinate geometry to two equivalent Er(1), four equivalent Er(2), two equivalent Tl(1), and two equivalent Tl(2) atoms.