ErFe6(Sn2Ge)2 crystallizes in the hexagonal P6/mmm space group. Er(1) is bonded to twelve equivalent Fe(1), two equivalent Sn(2), and six equivalent Ge(1) atoms to form distorted ErFe12Sn2Ge6 hexagonal bipyramids that share faces with twenty-four equivalent Fe(1)Er2Fe4Sn4Ge2 cuboctahedra and faces with six equivalent Er(1)Fe12Sn2Ge6 hexagonal bipyramids. Fe(1) is bonded to two equivalent Er(1), four equivalent Fe(1), two equivalent Sn(1), two equivalent Sn(2), and two equivalent Ge(1) atoms to form distorted FeEr2Fe4Sn4Ge2 cuboctahedra that share corners with fourteen equivalent Fe(1)Er2Fe4Sn4Ge2 cuboctahedra, edges with seven equivalent Fe(1)Er2Fe4Sn4Ge2 cuboctahedra, faces with nine equivalent Fe(1)Er2Fe4Sn4Ge2 cuboctahedra, and faces with four equivalent Er(1)Fe12Sn2Ge6 hexagonal bipyramids. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 6-coordinate geometry to six equivalent Fe(1) atoms. In the second Sn site, Sn(2) is bonded in a 8-coordinate geometry to one Er(1), six equivalent Fe(1), and one Sn(2) atom. Ge(1) is bonded in a 9-coordinate geometry to three equivalent Er(1) and six equivalent Fe(1) atoms.
ErFe6(Sn2Ge)2 crystallizes in the hexagonal P6/mmm space group. Er(1) is bonded to twelve equivalent Fe(1), two equivalent Sn(2), and six equivalent Ge(1) atoms to form distorted ErFe12Sn2Ge6 hexagonal bipyramids that share faces with twenty-four equivalent Fe(1)Er2Fe4Sn4Ge2 cuboctahedra and faces with six equivalent Er(1)Fe12Sn2Ge6 hexagonal bipyramids. All Er(1)-Fe(1) bond lengths are 3.33 Å. Both Er(1)-Sn(2) bond lengths are 2.93 Å. All Er(1)-Ge(1) bond lengths are 3.05 Å. Fe(1) is bonded to two equivalent Er(1), four equivalent Fe(1), two equivalent Sn(1), two equivalent Sn(2), and two equivalent Ge(1) atoms to form distorted FeEr2Fe4Sn4Ge2 cuboctahedra that share corners with fourteen equivalent Fe(1)Er2Fe4Sn4Ge2 cuboctahedra, edges with seven equivalent Fe(1)Er2Fe4Sn4Ge2 cuboctahedra, faces with nine equivalent Fe(1)Er2Fe4Sn4Ge2 cuboctahedra, and faces with four equivalent Er(1)Fe12Sn2Ge6 hexagonal bipyramids. All Fe(1)-Fe(1) bond lengths are 2.64 Å. Both Fe(1)-Sn(1) bond lengths are 2.79 Å. Both Fe(1)-Sn(2) bond lengths are 2.80 Å. Both Fe(1)-Ge(1) bond lengths are 2.53 Å. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 6-coordinate geometry to six equivalent Fe(1) atoms. In the second Sn site, Sn(2) is bonded in a 8-coordinate geometry to one Er(1), six equivalent Fe(1), and one Sn(2) atom. The Sn(2)-Sn(2) bond length is 2.85 Å. Ge(1) is bonded in a 9-coordinate geometry to three equivalent Er(1) and six equivalent Fe(1) atoms.