Ta4Fe4Si7 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in a 7-coordinate geometry to two equivalent Si(2), two equivalent Si(4), and three equivalent Si(1) atoms. In the second Ta site, Ta(2) is bonded in a 7-coordinate geometry to one Si(3), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(4) atoms. Fe(1) is bonded in a 6-coordinate geometry to two equivalent Si(1), two equivalent Si(2), and two equivalent Si(3) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Ta(2), three equivalent Ta(1), and four equivalent Fe(1) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Ta(1), two equivalent Ta(2), and four equivalent Fe(1) atoms. In the third Si site, Si(3) is bonded in a 6-coordinate geometry to one Ta(2), four equivalent Fe(1), and one Si(3) atom. In the fourth Si site, Si(4) is bonded in a 10-coordinate geometry to four equivalent Ta(1), four equivalent Ta(2), and two equivalent Si(4) atoms.
Ta4Fe4Si7 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in a 7-coordinate geometry to two equivalent Si(2), two equivalent Si(4), and three equivalent Si(1) atoms. Both Ta(1)-Si(2) bond lengths are 2.66 Å. Both Ta(1)-Si(4) bond lengths are 2.71 Å. There is one shorter (2.77 Å) and two longer (2.83 Å) Ta(1)-Si(1) bond lengths. In the second Ta site, Ta(2) is bonded in a 7-coordinate geometry to one Si(3), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(4) atoms. The Ta(2)-Si(3) bond length is 2.69 Å. Both Ta(2)-Si(1) bond lengths are 2.63 Å. Both Ta(2)-Si(2) bond lengths are 2.83 Å. Both Ta(2)-Si(4) bond lengths are 2.72 Å. Fe(1) is bonded in a 6-coordinate geometry to two equivalent Si(1), two equivalent Si(2), and two equivalent Si(3) atoms. Both Fe(1)-Si(1) bond lengths are 2.29 Å. Both Fe(1)-Si(2) bond lengths are 2.35 Å. Both Fe(1)-Si(3) bond lengths are 2.37 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Ta(2), three equivalent Ta(1), and four equivalent Fe(1) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to two equivalent Ta(1), two equivalent Ta(2), and four equivalent Fe(1) atoms. In the third Si site, Si(3) is bonded in a 6-coordinate geometry to one Ta(2), four equivalent Fe(1), and one Si(3) atom. The Si(3)-Si(3) bond length is 2.36 Å. In the fourth Si site, Si(4) is bonded in a 10-coordinate geometry to four equivalent Ta(1), four equivalent Ta(2), and two equivalent Si(4) atoms. There is one shorter (2.50 Å) and one longer (2.51 Å) Si(4)-Si(4) bond length.