Er11Ge10 is delta Molybdenum Boride-like structured and crystallizes in the tetragonal I4/mmm space group. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded to one Ge(1), one Ge(2), one Ge(4), and four equivalent Ge(5) atoms to form a mixture of distorted corner, edge, and face-sharing ErGe7 pentagonal bipyramids. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to one Ge(3), two equivalent Ge(1), two equivalent Ge(2), and two equivalent Ge(5) atoms. In the third Er site, Er(3) is bonded in a 9-coordinate geometry to one Ge(2), four equivalent Ge(3), and four equivalent Ge(5) atoms. In the fourth Er site, Er(4) is bonded in a 7-coordinate geometry to one Ge(4), two equivalent Ge(1), two equivalent Ge(3), and two equivalent Ge(5) atoms. There are five inequivalent Ge sites. In the first Ge site, Ge(1) is bonded in a 8-coordinate geometry to two equivalent Er(1), two equivalent Er(2), and four equivalent Er(4) atoms. In the second Ge site, Ge(2) is bonded in a 9-coordinate geometry to one Er(3), four equivalent Er(1), and four equivalent Er(2) atoms. In the third Ge site, Ge(3) is bonded in a 9-coordinate geometry to one Er(2), two equivalent Er(3), four equivalent Er(4), and two equivalent Ge(3) atoms. In the fourth Ge site, Ge(4) is bonded in a 8-coordinate geometry to four equivalent Er(1) and four equivalent Er(4) atoms. In the fifth Ge site, Ge(5) is bonded in a 9-coordinate geometry to one Er(2), one Er(3), two equivalent Er(4), four equivalent Er(1), and one Ge(5) atom.
Er11Ge10 is delta Molybdenum Boride-like structured and crystallizes in the tetragonal I4/mmm space group. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded to one Ge(1), one Ge(2), one Ge(4), and four equivalent Ge(5) atoms to form a mixture of distorted corner, edge, and face-sharing ErGe7 pentagonal bipyramids. The Er(1)-Ge(1) bond length is 3.28 Å. The Er(1)-Ge(2) bond length is 2.97 Å. The Er(1)-Ge(4) bond length is 2.84 Å. There are two shorter (3.10 Å) and two longer (3.17 Å) Er(1)-Ge(5) bond lengths. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to one Ge(3), two equivalent Ge(1), two equivalent Ge(2), and two equivalent Ge(5) atoms. The Er(2)-Ge(3) bond length is 3.09 Å. Both Er(2)-Ge(1) bond lengths are 2.72 Å. Both Er(2)-Ge(2) bond lengths are 3.29 Å. Both Er(2)-Ge(5) bond lengths are 3.42 Å. In the third Er site, Er(3) is bonded in a 9-coordinate geometry to one Ge(2), four equivalent Ge(3), and four equivalent Ge(5) atoms. The Er(3)-Ge(2) bond length is 3.62 Å. All Er(3)-Ge(3) bond lengths are 3.18 Å. All Er(3)-Ge(5) bond lengths are 3.20 Å. In the fourth Er site, Er(4) is bonded in a 7-coordinate geometry to one Ge(4), two equivalent Ge(1), two equivalent Ge(3), and two equivalent Ge(5) atoms. The Er(4)-Ge(4) bond length is 3.06 Å. Both Er(4)-Ge(1) bond lengths are 2.94 Å. Both Er(4)-Ge(3) bond lengths are 3.03 Å. Both Er(4)-Ge(5) bond lengths are 2.88 Å. There are five inequivalent Ge sites. In the first Ge site, Ge(1) is bonded in a 8-coordinate geometry to two equivalent Er(1), two equivalent Er(2), and four equivalent Er(4) atoms. In the second Ge site, Ge(2) is bonded in a 9-coordinate geometry to one Er(3), four equivalent Er(1), and four equivalent Er(2) atoms. In the third Ge site, Ge(3) is bonded in a 9-coordinate geometry to one Er(2), two equivalent Er(3), four equivalent Er(4), and two equivalent Ge(3) atoms. Both Ge(3)-Ge(3) bond lengths are 2.59 Å. In the fourth Ge site, Ge(4) is bonded in a 8-coordinate geometry to four equivalent Er(1) and four equivalent Er(4) atoms. In the fifth Ge site, Ge(5) is bonded in a 9-coordinate geometry to one Er(2), one Er(3), two equivalent Er(4), four equivalent Er(1), and one Ge(5) atom. The Ge(5)-Ge(5) bond length is 2.55 Å.