Mg3Tb2Ni2 crystallizes in the orthorhombic Cmmm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted single-bond geometry to four equivalent Mg(2) and one Ni(1) atom. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to eight equivalent Mg(1) and two equivalent Tb(1) atoms. Tb(1) is bonded in a 6-coordinate geometry to one Mg(2) and six equivalent Ni(1) atoms. Ni(1) is bonded in a 9-coordinate geometry to one Mg(1), six equivalent Tb(1), and two equivalent Ni(1) atoms.
Mg3Tb2Ni2 crystallizes in the orthorhombic Cmmm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted single-bond geometry to four equivalent Mg(2) and one Ni(1) atom. All Mg(1)-Mg(2) bond lengths are 3.16 Å. The Mg(1)-Ni(1) bond length is 2.82 Å. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to eight equivalent Mg(1) and two equivalent Tb(1) atoms. Both Mg(2)-Tb(1) bond lengths are 3.73 Å. Tb(1) is bonded in a 6-coordinate geometry to one Mg(2) and six equivalent Ni(1) atoms. There are four shorter (2.78 Å) and two longer (2.91 Å) Tb(1)-Ni(1) bond lengths. Ni(1) is bonded in a 9-coordinate geometry to one Mg(1), six equivalent Tb(1), and two equivalent Ni(1) atoms. Both Ni(1)-Ni(1) bond lengths are 2.50 Å.