Er3Ga2 crystallizes in the tetragonal I4/mcm space group. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded in a 4-coordinate geometry to two equivalent Ga(3) and four equivalent Ga(4) atoms. In the second Er site, Er(2) is bonded in a 5-coordinate geometry to two equivalent Ga(4) and three equivalent Ga(3) atoms. In the third Er site, Er(3) is bonded in a 6-coordinate geometry to one Ga(1), one Ga(2), one Ga(3), and three equivalent Ga(4) atoms. There are four inequivalent Ga sites. In the first Ga site, Ga(1) is bonded in a 8-coordinate geometry to eight equivalent Er(3) atoms. In the second Ga site, Ga(2) is bonded in a body-centered cubic geometry to eight equivalent Er(3) atoms. In the third Ga site, Ga(3) is bonded in a 9-coordinate geometry to two equivalent Er(1), three equivalent Er(2), and four equivalent Er(3) atoms. In the fourth Ga site, Ga(4) is bonded in a 10-coordinate geometry to one Er(2), two equivalent Er(1), six equivalent Er(3), and one Ga(4) atom.
Er3Ga2 crystallizes in the tetragonal I4/mcm space group. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded in a 4-coordinate geometry to two equivalent Ga(3) and four equivalent Ga(4) atoms. Both Er(1)-Ga(3) bond lengths are 2.86 Å. There are two shorter (2.99 Å) and two longer (3.65 Å) Er(1)-Ga(4) bond lengths. In the second Er site, Er(2) is bonded in a 5-coordinate geometry to two equivalent Ga(4) and three equivalent Ga(3) atoms. Both Er(2)-Ga(4) bond lengths are 2.94 Å. There are two shorter (3.32 Å) and one longer (3.48 Å) Er(2)-Ga(3) bond length. In the third Er site, Er(3) is bonded in a 6-coordinate geometry to one Ga(1), one Ga(2), one Ga(3), and three equivalent Ga(4) atoms. The Er(3)-Ga(1) bond length is 2.96 Å. The Er(3)-Ga(2) bond length is 3.15 Å. The Er(3)-Ga(3) bond length is 2.92 Å. There are a spread of Er(3)-Ga(4) bond distances ranging from 3.03-3.27 Å. There are four inequivalent Ga sites. In the first Ga site, Ga(1) is bonded in a 8-coordinate geometry to eight equivalent Er(3) atoms. In the second Ga site, Ga(2) is bonded in a body-centered cubic geometry to eight equivalent Er(3) atoms. In the third Ga site, Ga(3) is bonded in a 9-coordinate geometry to two equivalent Er(1), three equivalent Er(2), and four equivalent Er(3) atoms. In the fourth Ga site, Ga(4) is bonded in a 10-coordinate geometry to one Er(2), two equivalent Er(1), six equivalent Er(3), and one Ga(4) atom. The Ga(4)-Ga(4) bond length is 2.75 Å.