Tm3Cu4Sn4 crystallizes in the orthorhombic Immm space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to two equivalent Sn(1) and four equivalent Sn(2) atoms to form distorted edge-sharing TmSn6 octahedra. In the second Tm site, Tm(2) is bonded in a 12-coordinate geometry to six equivalent Cu(1), two equivalent Sn(1), and four equivalent Sn(2) atoms. Cu(1) is bonded in a 8-coordinate geometry to three equivalent Tm(2), one Cu(1), one Sn(2), and three equivalent Sn(1) atoms. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 9-coordinate geometry to one Tm(1), two equivalent Tm(2), and six equivalent Cu(1) atoms. In the second Sn site, Sn(2) is bonded in a 9-coordinate geometry to two equivalent Tm(1), four equivalent Tm(2), two equivalent Cu(1), and one Sn(2) atom.
Tm3Cu4Sn4 crystallizes in the orthorhombic Immm space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to two equivalent Sn(1) and four equivalent Sn(2) atoms to form distorted edge-sharing TmSn6 octahedra. Both Tm(1)-Sn(1) bond lengths are 3.14 Å. All Tm(1)-Sn(2) bond lengths are 3.00 Å. In the second Tm site, Tm(2) is bonded in a 12-coordinate geometry to six equivalent Cu(1), two equivalent Sn(1), and four equivalent Sn(2) atoms. There are four shorter (3.13 Å) and two longer (3.14 Å) Tm(2)-Cu(1) bond lengths. Both Tm(2)-Sn(1) bond lengths are 3.12 Å. All Tm(2)-Sn(2) bond lengths are 3.23 Å. Cu(1) is bonded in a 8-coordinate geometry to three equivalent Tm(2), one Cu(1), one Sn(2), and three equivalent Sn(1) atoms. The Cu(1)-Cu(1) bond length is 2.59 Å. The Cu(1)-Sn(2) bond length is 2.60 Å. There are two shorter (2.64 Å) and one longer (2.69 Å) Cu(1)-Sn(1) bond length. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 9-coordinate geometry to one Tm(1), two equivalent Tm(2), and six equivalent Cu(1) atoms. In the second Sn site, Sn(2) is bonded in a 9-coordinate geometry to two equivalent Tm(1), four equivalent Tm(2), two equivalent Cu(1), and one Sn(2) atom. The Sn(2)-Sn(2) bond length is 2.81 Å.