ErFe2Si2 crystallizes in the tetragonal I4/mmm space group. Er(1) is bonded in a 16-coordinate geometry to eight equivalent Fe(1) and eight equivalent Si(1) atoms. Fe(1) is bonded to four equivalent Er(1) and four equivalent Si(1) atoms to form a mixture of distorted edge, corner, and face-sharing FeEr4Si4 tetrahedra. Si(1) is bonded in a 9-coordinate geometry to four equivalent Er(1), four equivalent Fe(1), and one Si(1) atom.
ErFe2Si2 crystallizes in the tetragonal I4/mmm space group. Er(1) is bonded in a 16-coordinate geometry to eight equivalent Fe(1) and eight equivalent Si(1) atoms. All Er(1)-Fe(1) bond lengths are 3.12 Å. All Er(1)-Si(1) bond lengths are 3.00 Å. Fe(1) is bonded to four equivalent Er(1) and four equivalent Si(1) atoms to form a mixture of distorted edge, corner, and face-sharing FeEr4Si4 tetrahedra. All Fe(1)-Si(1) bond lengths are 2.27 Å. Si(1) is bonded in a 9-coordinate geometry to four equivalent Er(1), four equivalent Fe(1), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.49 Å.