Er11(In3Si2)2 crystallizes in the tetragonal I4/mmm space group. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded to four equivalent In(1), one Si(1), one Si(2), and one Si(3) atom to form a mixture of distorted edge, corner, and face-sharing ErIn4Si3 pentagonal bipyramids. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to two equivalent In(1), two equivalent In(2), one Si(3), and two equivalent Si(1) atoms. In the third Er site, Er(3) is bonded in a 7-coordinate geometry to one In(2), two equivalent In(1), two equivalent Si(1), and two equivalent Si(2) atoms. In the fourth Er site, Er(4) is bonded in a 9-coordinate geometry to four equivalent In(1), four equivalent In(2), and one Si(2) atom. There are two inequivalent In sites. In the first In site, In(1) is bonded in a 10-coordinate geometry to one Er(3), one Er(4), two equivalent Er(2), four equivalent Er(1), one In(1), and one In(2) atom. In the second In site, In(2) is bonded in a 11-coordinate geometry to one Er(3), two equivalent Er(4), four equivalent Er(2), two equivalent In(1), and two equivalent In(2) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent Er(1), two equivalent Er(3), and four equivalent Er(2) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Er(4), four equivalent Er(1), and four equivalent Er(3) atoms. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to four equivalent Er(1) and four equivalent Er(2) atoms.
Er11(In3Si2)2 crystallizes in the tetragonal I4/mmm space group. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded to four equivalent In(1), one Si(1), one Si(2), and one Si(3) atom to form a mixture of distorted edge, corner, and face-sharing ErIn4Si3 pentagonal bipyramids. There are two shorter (3.31 Å) and two longer (3.37 Å) Er(1)-In(1) bond lengths. The Er(1)-Si(1) bond length is 3.18 Å. The Er(1)-Si(2) bond length is 3.02 Å. The Er(1)-Si(3) bond length is 3.01 Å. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to two equivalent In(1), two equivalent In(2), one Si(3), and two equivalent Si(1) atoms. Both Er(2)-In(1) bond lengths are 3.04 Å. Both Er(2)-In(2) bond lengths are 3.30 Å. The Er(2)-Si(3) bond length is 2.95 Å. Both Er(2)-Si(1) bond lengths are 2.94 Å. In the third Er site, Er(3) is bonded in a 7-coordinate geometry to one In(2), two equivalent In(1), two equivalent Si(1), and two equivalent Si(2) atoms. The Er(3)-In(2) bond length is 3.27 Å. Both Er(3)-In(1) bond lengths are 3.40 Å. Both Er(3)-Si(1) bond lengths are 2.78 Å. Both Er(3)-Si(2) bond lengths are 3.31 Å. In the fourth Er site, Er(4) is bonded in a 9-coordinate geometry to four equivalent In(1), four equivalent In(2), and one Si(2) atom. All Er(4)-In(1) bond lengths are 3.30 Å. All Er(4)-In(2) bond lengths are 3.41 Å. The Er(4)-Si(2) bond length is 3.35 Å. There are two inequivalent In sites. In the first In site, In(1) is bonded in a 10-coordinate geometry to one Er(3), one Er(4), two equivalent Er(2), four equivalent Er(1), one In(1), and one In(2) atom. The In(1)-In(1) bond length is 2.91 Å. The In(1)-In(2) bond length is 3.00 Å. In the second In site, In(2) is bonded in a 11-coordinate geometry to one Er(3), two equivalent Er(4), four equivalent Er(2), two equivalent In(1), and two equivalent In(2) atoms. Both In(2)-In(2) bond lengths are 2.91 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent Er(1), two equivalent Er(3), and four equivalent Er(2) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Er(4), four equivalent Er(1), and four equivalent Er(3) atoms. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to four equivalent Er(1) and four equivalent Er(2) atoms.