TbFeSi2 crystallizes in the orthorhombic Cmcm space group. Tb(1) is bonded in a 14-coordinate geometry to four equivalent Fe(1), four equivalent Si(2), and six equivalent Si(1) atoms. Fe(1) is bonded in a 4-coordinate geometry to four equivalent Tb(1) and four equivalent Si(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to six equivalent Tb(1), one Si(2), and two equivalent Si(1) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to four equivalent Tb(1), four equivalent Fe(1), and one Si(1) atom.
TbFeSi2 crystallizes in the orthorhombic Cmcm space group. Tb(1) is bonded in a 14-coordinate geometry to four equivalent Fe(1), four equivalent Si(2), and six equivalent Si(1) atoms. There are two shorter (3.08 Å) and two longer (3.10 Å) Tb(1)-Fe(1) bond lengths. All Tb(1)-Si(2) bond lengths are 3.11 Å. There are four shorter (3.05 Å) and two longer (3.13 Å) Tb(1)-Si(1) bond lengths. Fe(1) is bonded in a 4-coordinate geometry to four equivalent Tb(1) and four equivalent Si(2) atoms. There are two shorter (2.24 Å) and two longer (2.27 Å) Fe(1)-Si(2) bond lengths. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to six equivalent Tb(1), one Si(2), and two equivalent Si(1) atoms. The Si(1)-Si(2) bond length is 2.47 Å. Both Si(1)-Si(1) bond lengths are 2.34 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to four equivalent Tb(1), four equivalent Fe(1), and one Si(1) atom.