Fe5Si3 crystallizes in the cubic Ia-3d space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted linear geometry to four equivalent Fe(2) and six equivalent Si(1) atoms. In the second Fe site, Fe(2) is bonded to six equivalent Fe(1) and six equivalent Si(1) atoms to form a mixture of edge and face-sharing FeFe6Si6 cuboctahedra. Si(1) is bonded in a 14-coordinate geometry to four equivalent Fe(2), six equivalent Fe(1), and four equivalent Si(1) atoms.
Fe5Si3 crystallizes in the cubic Ia-3d space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted linear geometry to four equivalent Fe(2) and six equivalent Si(1) atoms. All Fe(1)-Fe(2) bond lengths are 2.49 Å. There are two shorter (2.22 Å) and four longer (2.72 Å) Fe(1)-Si(1) bond lengths. In the second Fe site, Fe(2) is bonded to six equivalent Fe(1) and six equivalent Si(1) atoms to form a mixture of edge and face-sharing FeFe6Si6 cuboctahedra. All Fe(2)-Si(1) bond lengths are 2.49 Å. Si(1) is bonded in a 14-coordinate geometry to four equivalent Fe(2), six equivalent Fe(1), and four equivalent Si(1) atoms. All Si(1)-Si(1) bond lengths are 2.72 Å.