TlSr3Fe2O8 crystallizes in the orthorhombic Pmm2 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to one O(5), two equivalent O(1), two equivalent O(2), and four equivalent O(4) atoms. In the second Sr site, Sr(2) is bonded to four equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms to form SrO12 cuboctahedra that share corners with four equivalent Sr(2)O12 cuboctahedra, faces with four equivalent Sr(2)O12 cuboctahedra, and faces with eight equivalent Fe(1)O6 octahedra. Fe(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form FeO6 octahedra that share corners with five equivalent Fe(1)O6 octahedra and faces with four equivalent Sr(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-5°. Tl(1) is bonded in a see-saw-like geometry to two equivalent O(4) and two equivalent O(5) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with four equivalent O(1)Sr4Fe2 octahedra, corners with four equivalent O(2)Sr4Fe2 octahedra, corners with four equivalent O(3)Sr4Fe2 octahedra, corners with four equivalent O(4)Sr4TlFe octahedra, edges with three equivalent O(1)Sr4Fe2 octahedra, faces with two equivalent O(3)Sr4Fe2 octahedra, faces with two equivalent O(4)Sr4TlFe octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the second O site, O(2) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with four equivalent O(1)Sr4Fe2 octahedra, corners with four equivalent O(2)Sr4Fe2 octahedra, corners with four equivalent O(3)Sr4Fe2 octahedra, corners with four equivalent O(4)Sr4TlFe octahedra, edges with three equivalent O(2)Sr4Fe2 octahedra, faces with two equivalent O(3)Sr4Fe2 octahedra, faces with two equivalent O(4)Sr4TlFe octahedra, and faces with four equivalent O(1)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the third O site, O(3) is bonded to four equivalent Sr(2) and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with two equivalent O(4)Sr4TlFe octahedra, corners with four equivalent O(3)Sr4Fe2 octahedra, corners with eight equivalent O(1)Sr4Fe2 octahedra, corners with eight equivalent O(2)Sr4Fe2 octahedra, edges with four equivalent O(3)Sr4Fe2 octahedra, faces with four equivalent O(1)Sr4Fe2 octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the fourth O site, O(4) is bonded to four equivalent Sr(1), one Fe(1), and one Tl(1) atom to form distorted OSr4TlFe octahedra that share  a cornercorner with one O(3)Sr4Fe2 octahedra, corners with four equivalent O(1)Sr4Fe2 octahedra, corners with four equivalent O(2)Sr4Fe2 octahedra, corners with five equivalent O(4)Sr4TlFe octahedra, edges with four equivalent O(4)Sr4TlFe octahedra, faces with two equivalent O(1)Sr4Fe2 octahedra, and faces with two equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 2-53°. In the fifth O site, O(5) is bonded in a see-saw-like geometry to two equivalent Sr(1) and two equivalent Tl(1) atoms.
TlSr3Fe2O8 crystallizes in the orthorhombic Pmm2 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to one O(5), two equivalent O(1), two equivalent O(2), and four equivalent O(4) atoms. The Sr(1)-O(5) bond length is 2.55 Å. There is one shorter (2.63 Å) and one longer (2.64 Å) Sr(1)-O(1) bond length. Both Sr(1)-O(2) bond lengths are 2.63 Å. There are two shorter (2.73 Å) and two longer (2.83 Å) Sr(1)-O(4) bond lengths. In the second Sr site, Sr(2) is bonded to four equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms to form SrO12 cuboctahedra that share corners with four equivalent Sr(2)O12 cuboctahedra, faces with four equivalent Sr(2)O12 cuboctahedra, and faces with eight equivalent Fe(1)O6 octahedra. There are two shorter (2.82 Å) and two longer (2.83 Å) Sr(2)-O(1) bond lengths. All Sr(2)-O(2) bond lengths are 2.83 Å. All Sr(2)-O(3) bond lengths are 2.75 Å. Fe(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form FeO6 octahedra that share corners with five equivalent Fe(1)O6 octahedra and faces with four equivalent Sr(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-5°. The Fe(1)-O(3) bond length is 1.97 Å. The Fe(1)-O(4) bond length is 2.26 Å. Both Fe(1)-O(1) bond lengths are 1.94 Å. Both Fe(1)-O(2) bond lengths are 1.95 Å. Tl(1) is bonded in a see-saw-like geometry to two equivalent O(4) and two equivalent O(5) atoms. Both Tl(1)-O(4) bond lengths are 2.14 Å. Both Tl(1)-O(5) bond lengths are 2.35 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with four equivalent O(1)Sr4Fe2 octahedra, corners with four equivalent O(2)Sr4Fe2 octahedra, corners with four equivalent O(3)Sr4Fe2 octahedra, corners with four equivalent O(4)Sr4TlFe octahedra, edges with three equivalent O(1)Sr4Fe2 octahedra, faces with two equivalent O(3)Sr4Fe2 octahedra, faces with two equivalent O(4)Sr4TlFe octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the second O site, O(2) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with four equivalent O(1)Sr4Fe2 octahedra, corners with four equivalent O(2)Sr4Fe2 octahedra, corners with four equivalent O(3)Sr4Fe2 octahedra, corners with four equivalent O(4)Sr4TlFe octahedra, edges with three equivalent O(2)Sr4Fe2 octahedra, faces with two equivalent O(3)Sr4Fe2 octahedra, faces with two equivalent O(4)Sr4TlFe octahedra, and faces with four equivalent O(1)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the third O site, O(3) is bonded to four equivalent Sr(2) and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with two equivalent O(4)Sr4TlFe octahedra, corners with four equivalent O(3)Sr4Fe2 octahedra, corners with eight equivalent O(1)Sr4Fe2 octahedra, corners with eight equivalent O(2)Sr4Fe2 octahedra, edges with four equivalent O(3)Sr4Fe2 octahedra, faces with four equivalent O(1)Sr4Fe2 octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-61°. In the fourth O site, O(4) is bonded to four equivalent Sr(1), one Fe(1), and one Tl(1) atom to form distorted OSr4TlFe octahedra that share  a cornercorner with one O(3)Sr4Fe2 octahedra, corners with four equivalent O(1)Sr4Fe2 octahedra, corners with four equivalent O(2)Sr4Fe2 octahedra, corners with five equivalent O(4)Sr4TlFe octahedra, edges with four equivalent O(4)Sr4TlFe octahedra, faces with two equivalent O(1)Sr4Fe2 octahedra, and faces with two equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 2-53°. In the fifth O site, O(5) is bonded in a see-saw-like geometry to two equivalent Sr(1) and two equivalent Tl(1) atoms.