TlSr4Fe2O9 crystallizes in the orthorhombic Fmm2 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(4), four equivalent O(1), and four equivalent O(2) atoms. In the second Sr site, Sr(2) is bonded in a 9-coordinate geometry to four equivalent O(2) and five equivalent O(3) atoms. Fe(1) is bonded to one O(1), one O(3), and four equivalent O(2) atoms to form distorted FeO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra and  a cornercorner with one Tl(1)O5 square pyramid. The corner-sharing octahedral tilt angles are 10°. Tl(1) is bonded to two equivalent O(1) and three equivalent O(4) atoms to form distorted TlO5 square pyramids that share corners with two equivalent Fe(1)O6 octahedra and corners with six equivalent Tl(1)O5 square pyramids. The corner-sharing octahedral tilt angles are 6°. There are four inequivalent O sites. In the first O site, O(3) is bonded to five equivalent Sr(2) and one Fe(1) atom to form distorted OSr5Fe octahedra that share  a cornercorner with one O(1)Sr4TlFe octahedra, corners with four equivalent O(3)Sr5Fe octahedra, corners with twelve equivalent O(2)Sr4Fe2 octahedra, edges with eight equivalent O(3)Sr5Fe octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 1-56°. In the second O site, O(4) is bonded to two equivalent Sr(1) and three equivalent Tl(1) atoms to form distorted OSr2Tl3 square pyramids that share corners with two equivalent O(1)Sr4TlFe octahedra, corners with eight equivalent O(2)Sr4Fe2 octahedra, corners with six equivalent O(4)Sr2Tl3 square pyramids, and edges with six equivalent O(1)Sr4TlFe octahedra. The corner-sharing octahedral tilt angles range from 42-93°. In the third O site, O(1) 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)Sr5Fe octahedra, corners with five equivalent O(1)Sr4TlFe octahedra, corners with eight equivalent O(2)Sr4Fe2 octahedra,  a cornercorner with one O(4)Sr2Tl3 square pyramid, edges with four equivalent O(1)Sr4TlFe octahedra, edges with three equivalent O(4)Sr2Tl3 square pyramids, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 1-53°. In the fourth 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 two equivalent O(2)Sr4Fe2 octahedra, corners with four equivalent O(1)Sr4TlFe octahedra, corners with six equivalent O(3)Sr5Fe octahedra, corners with two equivalent O(4)Sr2Tl3 square pyramids, edges with two equivalent O(2)Sr4Fe2 octahedra, faces with two equivalent O(1)Sr4TlFe octahedra, faces with two equivalent O(3)Sr5Fe octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 10-56°.
TlSr4Fe2O9 crystallizes in the orthorhombic Fmm2 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(4), four equivalent O(1), and four equivalent O(2) atoms. The Sr(1)-O(4) bond length is 2.53 Å. There are a spread of Sr(1)-O(1) bond distances ranging from 2.73-2.80 Å. All Sr(1)-O(2) bond lengths are 2.68 Å. In the second Sr site, Sr(2) is bonded in a 9-coordinate geometry to four equivalent O(2) and five equivalent O(3) atoms. All Sr(2)-O(2) bond lengths are 2.71 Å. There are a spread of Sr(2)-O(3) bond distances ranging from 2.50-2.75 Å. Fe(1) is bonded to one O(1), one O(3), and four equivalent O(2) atoms to form distorted FeO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra and  a cornercorner with one Tl(1)O5 square pyramid. The corner-sharing octahedral tilt angles are 10°. The Fe(1)-O(1) bond length is 2.44 Å. The Fe(1)-O(3) bond length is 1.97 Å. All Fe(1)-O(2) bond lengths are 1.93 Å. Tl(1) is bonded to two equivalent O(1) and three equivalent O(4) atoms to form distorted TlO5 square pyramids that share corners with two equivalent Fe(1)O6 octahedra and corners with six equivalent Tl(1)O5 square pyramids. The corner-sharing octahedral tilt angles are 6°. Both Tl(1)-O(1) bond lengths are 2.11 Å. There is one shorter (2.35 Å) and two longer (2.74 Å) Tl(1)-O(4) bond lengths. There are four inequivalent O sites. In the first O site, O(3) is bonded to five equivalent Sr(2) and one Fe(1) atom to form distorted OSr5Fe octahedra that share  a cornercorner with one O(1)Sr4TlFe octahedra, corners with four equivalent O(3)Sr5Fe octahedra, corners with twelve equivalent O(2)Sr4Fe2 octahedra, edges with eight equivalent O(3)Sr5Fe octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 1-56°. In the second O site, O(4) is bonded to two equivalent Sr(1) and three equivalent Tl(1) atoms to form distorted OSr2Tl3 square pyramids that share corners with two equivalent O(1)Sr4TlFe octahedra, corners with eight equivalent O(2)Sr4Fe2 octahedra, corners with six equivalent O(4)Sr2Tl3 square pyramids, and edges with six equivalent O(1)Sr4TlFe octahedra. The corner-sharing octahedral tilt angles range from 42-93°. In the third O site, O(1) 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)Sr5Fe octahedra, corners with five equivalent O(1)Sr4TlFe octahedra, corners with eight equivalent O(2)Sr4Fe2 octahedra,  a cornercorner with one O(4)Sr2Tl3 square pyramid, edges with four equivalent O(1)Sr4TlFe octahedra, edges with three equivalent O(4)Sr2Tl3 square pyramids, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 1-53°. In the fourth 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 two equivalent O(2)Sr4Fe2 octahedra, corners with four equivalent O(1)Sr4TlFe octahedra, corners with six equivalent O(3)Sr5Fe octahedra, corners with two equivalent O(4)Sr2Tl3 square pyramids, edges with two equivalent O(2)Sr4Fe2 octahedra, faces with two equivalent O(1)Sr4TlFe octahedra, faces with two equivalent O(3)Sr5Fe octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 10-56°.