Tb2Si3 crystallizes in the hexagonal P-6m2 space group. Tb(1) is bonded in a 9-coordinate geometry to three equivalent Si(1), three equivalent Si(2), and three equivalent Si(3) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to six equivalent Tb(1) and three equivalent Si(3) atoms. In the second Si site, Si(2) is bonded to six equivalent Tb(1) atoms to form distorted edge-sharing SiTb6 pentagonal pyramids. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to six equivalent Tb(1) and three equivalent Si(1) atoms.
Tb2Si3 crystallizes in the hexagonal P-6m2 space group. Tb(1) is bonded in a 9-coordinate geometry to three equivalent Si(1), three equivalent Si(2), and three equivalent Si(3) atoms. All Tb(1)-Si(1) bond lengths are 3.07 Å. All Tb(1)-Si(2) bond lengths are 3.01 Å. All Tb(1)-Si(3) bond lengths are 3.07 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to six equivalent Tb(1) and three equivalent Si(3) atoms. All Si(1)-Si(3) bond lengths are 2.30 Å. In the second Si site, Si(2) is bonded to six equivalent Tb(1) atoms to form distorted edge-sharing SiTb6 pentagonal pyramids. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to six equivalent Tb(1) and three equivalent Si(1) atoms.