Er(FeB)2 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 B(1) atoms. Fe(1) is bonded to four equivalent Er(1) and four equivalent B(1) atoms to form a mixture of distorted face, corner, and edge-sharing FeEr4B4 tetrahedra. B(1) is bonded in a 9-coordinate geometry to four equivalent Er(1), four equivalent Fe(1), and one B(1) atom.
Er(FeB)2 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 B(1) atoms. All Er(1)-Fe(1) bond lengths are 2.93 Å. All Er(1)-B(1) bond lengths are 2.67 Å. Fe(1) is bonded to four equivalent Er(1) and four equivalent B(1) atoms to form a mixture of distorted face, corner, and edge-sharing FeEr4B4 tetrahedra. All Fe(1)-B(1) bond lengths are 2.16 Å. B(1) is bonded in a 9-coordinate geometry to four equivalent Er(1), four equivalent Fe(1), and one B(1) atom. The B(1)-B(1) bond length is 2.15 Å.