Tb2Al3Si2 crystallizes in the monoclinic C2/m space group. Tb(1) is bonded in a 11-coordinate geometry to two equivalent Al(2), four equivalent Al(1), and five equivalent Si(1) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 2-coordinate geometry to four equivalent Tb(1) and two equivalent Si(1) atoms. In the second Al site, Al(2) is bonded in a 6-coordinate geometry to four equivalent Tb(1) and two equivalent Si(1) atoms. Si(1) is bonded in a 9-coordinate geometry to five equivalent Tb(1), one Al(2), two equivalent Al(1), and one Si(1) atom.
Tb2Al3Si2 crystallizes in the monoclinic C2/m space group. Tb(1) is bonded in a 11-coordinate geometry to two equivalent Al(2), four equivalent Al(1), and five equivalent Si(1) atoms. Both Tb(1)-Al(2) bond lengths are 3.02 Å. There are a spread of Tb(1)-Al(1) bond distances ranging from 3.19-3.24 Å. There are a spread of Tb(1)-Si(1) bond distances ranging from 2.89-3.00 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 2-coordinate geometry to four equivalent Tb(1) and two equivalent Si(1) atoms. Both Al(1)-Si(1) bond lengths are 2.61 Å. In the second Al site, Al(2) is bonded in a 6-coordinate geometry to four equivalent Tb(1) and two equivalent Si(1) atoms. Both Al(2)-Si(1) bond lengths are 2.71 Å. Si(1) is bonded in a 9-coordinate geometry to five equivalent Tb(1), one Al(2), two equivalent Al(1), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.37 Å.