TmB4 crystallizes in the tetragonal P4/mbm space group. Tm(1) is bonded in a 18-coordinate geometry to four equivalent B(2), six equivalent B(1), and eight equivalent B(3) atoms. There are three inequivalent B sites. In the first B site, B(1) is bonded in a distorted trigonal planar geometry to six equivalent Tm(1), one B(1), and two equivalent B(3) atoms. In the second B site, B(2) is bonded in a 9-coordinate geometry to four equivalent Tm(1), one B(2), and four equivalent B(3) atoms. In the third B site, B(3) is bonded in a 9-coordinate geometry to four equivalent Tm(1), one B(1), two equivalent B(2), and two equivalent B(3) atoms.
TmB4 crystallizes in the tetragonal P4/mbm space group. Tm(1) is bonded in a 18-coordinate geometry to four equivalent B(2), six equivalent B(1), and eight equivalent B(3) atoms. All Tm(1)-B(2) bond lengths are 2.70 Å. There are four shorter (2.82 Å) and two longer (3.05 Å) Tm(1)-B(1) bond lengths. There are four shorter (2.71 Å) and four longer (2.80 Å) Tm(1)-B(3) bond lengths. There are three inequivalent B sites. In the first B site, B(1) is bonded in a distorted trigonal planar geometry to six equivalent Tm(1), one B(1), and two equivalent B(3) atoms. The B(1)-B(1) bond length is 1.73 Å. Both B(1)-B(3) bond lengths are 1.70 Å. In the second B site, B(2) is bonded in a 9-coordinate geometry to four equivalent Tm(1), one B(2), and four equivalent B(3) atoms. The B(2)-B(2) bond length is 1.61 Å. All B(2)-B(3) bond lengths are 1.74 Å. In the third B site, B(3) is bonded in a 9-coordinate geometry to four equivalent Tm(1), one B(1), two equivalent B(2), and two equivalent B(3) atoms. Both B(3)-B(3) bond lengths are 1.80 Å.