FeNiSb4 is Marcasite-derived structured and crystallizes in the monoclinic P2/m space group. Fe(1) is bonded to two equivalent Sb(1) and four equivalent Sb(2) atoms to form FeSb6 octahedra that share corners with eight equivalent Ni(1)Sb6 octahedra and edges with two equivalent Fe(1)Sb6 octahedra. The corner-sharing octahedral tilt angles range from 52-53°. Ni(1) is bonded to two equivalent Sb(2) and four equivalent Sb(1) atoms to form NiSb6 octahedra that share corners with eight equivalent Fe(1)Sb6 octahedra and edges with two equivalent Ni(1)Sb6 octahedra. The corner-sharing octahedral tilt angles range from 52-53°. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded in a 3-coordinate geometry to one Fe(1) and two equivalent Ni(1) atoms. In the second Sb site, Sb(2) is bonded in a 3-coordinate geometry to two equivalent Fe(1) and one Ni(1) atom.
FeNiSb4 is Marcasite-derived structured and crystallizes in the monoclinic P2/m space group. Fe(1) is bonded to two equivalent Sb(1) and four equivalent Sb(2) atoms to form FeSb6 octahedra that share corners with eight equivalent Ni(1)Sb6 octahedra and edges with two equivalent Fe(1)Sb6 octahedra. The corner-sharing octahedral tilt angles range from 52-53°. Both Fe(1)-Sb(1) bond lengths are 2.54 Å. All Fe(1)-Sb(2) bond lengths are 2.57 Å. Ni(1) is bonded to two equivalent Sb(2) and four equivalent Sb(1) atoms to form NiSb6 octahedra that share corners with eight equivalent Fe(1)Sb6 octahedra and edges with two equivalent Ni(1)Sb6 octahedra. The corner-sharing octahedral tilt angles range from 52-53°. Both Ni(1)-Sb(2) bond lengths are 2.60 Å. All Ni(1)-Sb(1) bond lengths are 2.60 Å. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded in a 3-coordinate geometry to one Fe(1) and two equivalent Ni(1) atoms. In the second Sb site, Sb(2) is bonded in a 3-coordinate geometry to two equivalent Fe(1) and one Ni(1) atom.