TiFeSi2 crystallizes in the orthorhombic Pbam space group. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent Fe(2), four equivalent Fe(1), two equivalent Si(2), two equivalent Si(5), and three equivalent Si(3) atoms to form distorted TiFe6Si7 pentagonal bipyramids that share corners with two equivalent Ti(1)Fe6Si7 pentagonal bipyramids, edges with two equivalent Fe(2)Ti4Fe2Si6 cuboctahedra, faces with two equivalent Fe(2)Ti4Fe2Si6 cuboctahedra, and faces with three equivalent Ti(1)Fe6Si7 pentagonal bipyramids. In the second Ti site, Ti(2) is bonded in a 8-coordinate geometry to one Fe(2), three equivalent Fe(1), one Si(3), one Si(4), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(5) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 12-coordinate geometry to two equivalent Ti(1), three equivalent Ti(2), one Fe(2), one Si(1), one Si(2), one Si(3), one Si(4), and two equivalent Si(5) atoms. In the second Fe site, Fe(2) is bonded to two equivalent Ti(1), two equivalent Ti(2), two equivalent Fe(1), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(5) atoms to form distorted FeTi4Fe2Si6 cuboctahedra that share  an edgeedge with one Fe(2)Ti4Fe2Si6 cuboctahedra, edges with two equivalent Ti(1)Fe6Si7 pentagonal bipyramids,  a faceface with one Fe(2)Ti4Fe2Si6 cuboctahedra, and faces with two equivalent Ti(1)Fe6Si7 pentagonal bipyramids. There are five inequivalent Si sites. In the first Si site, Si(4) is bonded in a 6-coordinate geometry to two equivalent Ti(2), two equivalent Fe(1), and two equivalent Fe(2) atoms. In the second Si site, Si(5) is bonded in a 7-coordinate geometry to one Ti(1), two equivalent Ti(2), one Fe(2), two equivalent Fe(1), and one Si(5) atom. In the third Si site, Si(1) is bonded in a 7-coordinate geometry to four equivalent Ti(2), two equivalent Fe(1), and one Si(1) atom. In the fourth Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Ti(1), four equivalent Ti(2), two equivalent Fe(1), and one Si(2) atom. In the fifth Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Ti(2), three equivalent Ti(1), two equivalent Fe(1), and two equivalent Fe(2) atoms.
TiFeSi2 crystallizes in the orthorhombic Pbam space group. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent Fe(2), four equivalent Fe(1), two equivalent Si(2), two equivalent Si(5), and three equivalent Si(3) atoms to form distorted TiFe6Si7 pentagonal bipyramids that share corners with two equivalent Ti(1)Fe6Si7 pentagonal bipyramids, edges with two equivalent Fe(2)Ti4Fe2Si6 cuboctahedra, faces with two equivalent Fe(2)Ti4Fe2Si6 cuboctahedra, and faces with three equivalent Ti(1)Fe6Si7 pentagonal bipyramids. Both Ti(1)-Fe(2) bond lengths are 2.91 Å. There are two shorter (2.90 Å) and two longer (2.98 Å) Ti(1)-Fe(1) bond lengths. Both Ti(1)-Si(2) bond lengths are 2.57 Å. Both Ti(1)-Si(5) bond lengths are 2.65 Å. There are a spread of Ti(1)-Si(3) bond distances ranging from 2.64-2.68 Å. In the second Ti site, Ti(2) is bonded in a 8-coordinate geometry to one Fe(2), three equivalent Fe(1), one Si(3), one Si(4), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(5) atoms. The Ti(2)-Fe(2) bond length is 2.86 Å. There are a spread of Ti(2)-Fe(1) bond distances ranging from 2.83-2.93 Å. The Ti(2)-Si(3) bond length is 2.58 Å. The Ti(2)-Si(4) bond length is 2.69 Å. There is one shorter (2.78 Å) and one longer (2.79 Å) Ti(2)-Si(1) bond length. There is one shorter (2.64 Å) and one longer (2.65 Å) Ti(2)-Si(2) bond length. There is one shorter (2.68 Å) and one longer (2.69 Å) Ti(2)-Si(5) bond length. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 12-coordinate geometry to two equivalent Ti(1), three equivalent Ti(2), one Fe(2), one Si(1), one Si(2), one Si(3), one Si(4), and two equivalent Si(5) atoms. The Fe(1)-Fe(2) bond length is 2.45 Å. The Fe(1)-Si(1) bond length is 2.29 Å. The Fe(1)-Si(2) bond length is 2.29 Å. The Fe(1)-Si(3) bond length is 2.37 Å. The Fe(1)-Si(4) bond length is 2.43 Å. There is one shorter (2.33 Å) and one longer (2.38 Å) Fe(1)-Si(5) bond length. In the second Fe site, Fe(2) is bonded to two equivalent Ti(1), two equivalent Ti(2), two equivalent Fe(1), two equivalent Si(3), two equivalent Si(4), and two equivalent Si(5) atoms to form distorted FeTi4Fe2Si6 cuboctahedra that share  an edgeedge with one Fe(2)Ti4Fe2Si6 cuboctahedra, edges with two equivalent Ti(1)Fe6Si7 pentagonal bipyramids,  a faceface with one Fe(2)Ti4Fe2Si6 cuboctahedra, and faces with two equivalent Ti(1)Fe6Si7 pentagonal bipyramids. Both Fe(2)-Si(3) bond lengths are 2.37 Å. Both Fe(2)-Si(4) bond lengths are 2.40 Å. Both Fe(2)-Si(5) bond lengths are 2.36 Å. There are five inequivalent Si sites. In the first Si site, Si(4) is bonded in a 6-coordinate geometry to two equivalent Ti(2), two equivalent Fe(1), and two equivalent Fe(2) atoms. In the second Si site, Si(5) is bonded in a 7-coordinate geometry to one Ti(1), two equivalent Ti(2), one Fe(2), two equivalent Fe(1), and one Si(5) atom. The Si(5)-Si(5) bond length is 2.34 Å. In the third Si site, Si(1) is bonded in a 7-coordinate geometry to four equivalent Ti(2), two equivalent Fe(1), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.42 Å. In the fourth Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Ti(1), four equivalent Ti(2), two equivalent Fe(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.37 Å. In the fifth Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Ti(2), three equivalent Ti(1), two equivalent Fe(1), and two equivalent Fe(2) atoms.