GdTiFe9Si2 crystallizes in the monoclinic Cm space group. Gd(1) is bonded in a 20-coordinate geometry to one Ti(1), one Fe(6), one Fe(7), one Fe(8), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(4), four equivalent Fe(5), and four equivalent Si(1) atoms. Ti(1) is bonded in a 14-coordinate geometry to one Gd(1), one Fe(1), one Fe(2), one Fe(8), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(6), two equivalent Fe(7), and two equivalent Si(1) atoms. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ti(1), one Fe(3), one Fe(4), one Fe(8), two equivalent Fe(5), two equivalent Fe(7), and two equivalent Si(1) atoms. In the second Fe site, Fe(2) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ti(1), one Fe(3), one Fe(4), one Fe(8), two equivalent Fe(5), two equivalent Fe(6), and two equivalent Si(1) atoms. In the third Fe site, Fe(3) is bonded to two equivalent Gd(1), two equivalent Ti(1), one Fe(1), one Fe(2), one Fe(6), one Fe(7), two equivalent Fe(5), and two equivalent Si(1) atoms to form distorted FeGd2Ti2Fe6Si2 cuboctahedra that share corners with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, corners with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra, corners with six equivalent Fe(4)Gd2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(4)Gd2Fe8Si2 cuboctahedra, edges with two equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, edges with two equivalent Fe(5)Gd2TiFe9 cuboctahedra, edges with two equivalent Si(1)Gd2TiFe7Si2 cuboctahedra,  a faceface with one Fe(4)Gd2Fe8Si2 cuboctahedra, faces with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, and faces with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra. In the fourth Fe site, Fe(4) is bonded to two equivalent Gd(1), one Fe(1), one Fe(2), one Fe(6), one Fe(7), two equivalent Fe(5), two equivalent Fe(8), and two equivalent Si(1) atoms to form distorted FeGd2Fe8Si2 cuboctahedra that share corners with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, corners with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra, corners with six equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra,  an edgeedge with one Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, edges with two equivalent Fe(4)Gd2Fe8Si2 cuboctahedra, edges with two equivalent Fe(5)Gd2TiFe9 cuboctahedra, edges with two equivalent Si(1)Gd2TiFe7Si2 cuboctahedra,  a faceface with one Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, faces with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, and faces with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra. In the fifth Fe site, Fe(5) is bonded to two equivalent Gd(1), one Ti(1), one Fe(1), one Fe(2), one Fe(3), one Fe(4), one Fe(6), one Fe(7), one Fe(8), and two equivalent Fe(5) atoms to form distorted FeGd2TiFe9 cuboctahedra that share corners with two equivalent Fe(4)Gd2Fe8Si2 cuboctahedra, corners with two equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, corners with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra, corners with six equivalent Fe(5)Gd2TiFe9 cuboctahedra,  an edgeedge with one Fe(4)Gd2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, edges with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra, faces with two equivalent Fe(4)Gd2Fe8Si2 cuboctahedra, faces with two equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, faces with two equivalent Fe(5)Gd2TiFe9 cuboctahedra, and faces with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra. In the sixth Fe site, Fe(6) is bonded in a 12-coordinate geometry to one Gd(1), two equivalent Ti(1), one Fe(3), one Fe(4), one Fe(7), two equivalent Fe(2), two equivalent Fe(5), and two equivalent Si(1) atoms. In the seventh Fe site, Fe(7) is bonded in a 14-coordinate geometry to one Gd(1), two equivalent Ti(1), one Fe(3), one Fe(4), one Fe(6), two equivalent Fe(1), two equivalent Fe(5), two equivalent Fe(8), and two equivalent Si(1) atoms. In the eighth Fe site, Fe(8) is bonded in a 1-coordinate geometry to one Gd(1), one Ti(1), one Fe(1), one Fe(2), two equivalent Fe(4), two equivalent Fe(5), two equivalent Fe(7), and two equivalent Si(1) atoms. Si(1) is bonded to two equivalent Gd(1), one Ti(1), one Fe(1), one Fe(2), one Fe(3), one Fe(4), one Fe(6), one Fe(7), one Fe(8), and two equivalent Si(1) atoms to form distorted SiGd2TiFe7Si2 cuboctahedra that share corners with two equivalent Fe(4)Gd2Fe8Si2 cuboctahedra, corners with two equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, corners with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, corners with six equivalent Si(1)Gd2TiFe7Si2 cuboctahedra,  an edgeedge with one Fe(4)Gd2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, edges with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, faces with two equivalent Fe(4)Gd2Fe8Si2 cuboctahedra, faces with two equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, faces with two equivalent Si(1)Gd2TiFe7Si2 cuboctahedra, and faces with four equivalent Fe(5)Gd2TiFe9 cuboctahedra.
GdTiFe9Si2 crystallizes in the monoclinic Cm space group. Gd(1) is bonded in a 20-coordinate geometry to one Ti(1), one Fe(6), one Fe(7), one Fe(8), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(4), four equivalent Fe(5), and four equivalent Si(1) atoms. The Gd(1)-Ti(1) bond length is 3.13 Å. The Gd(1)-Fe(6) bond length is 2.96 Å. The Gd(1)-Fe(7) bond length is 2.97 Å. The Gd(1)-Fe(8) bond length is 2.89 Å. Both Gd(1)-Fe(1) bond lengths are 2.98 Å. Both Gd(1)-Fe(2) bond lengths are 3.01 Å. Both Gd(1)-Fe(3) bond lengths are 3.06 Å. Both Gd(1)-Fe(4) bond lengths are 3.03 Å. There are two shorter (3.17 Å) and two longer (3.21 Å) Gd(1)-Fe(5) bond lengths. There are two shorter (3.12 Å) and two longer (3.19 Å) Gd(1)-Si(1) bond lengths. Ti(1) is bonded in a 14-coordinate geometry to one Gd(1), one Fe(1), one Fe(2), one Fe(8), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(6), two equivalent Fe(7), and two equivalent Si(1) atoms. The Ti(1)-Fe(1) bond length is 2.60 Å. The Ti(1)-Fe(2) bond length is 2.59 Å. The Ti(1)-Fe(8) bond length is 2.27 Å. Both Ti(1)-Fe(3) bond lengths are 2.70 Å. Both Ti(1)-Fe(5) bond lengths are 2.59 Å. Both Ti(1)-Fe(6) bond lengths are 2.87 Å. Both Ti(1)-Fe(7) bond lengths are 2.88 Å. Both Ti(1)-Si(1) bond lengths are 2.68 Å. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ti(1), one Fe(3), one Fe(4), one Fe(8), two equivalent Fe(5), two equivalent Fe(7), and two equivalent Si(1) atoms. The Fe(1)-Fe(3) bond length is 2.58 Å. The Fe(1)-Fe(4) bond length is 2.55 Å. The Fe(1)-Fe(8) bond length is 2.63 Å. Both Fe(1)-Fe(5) bond lengths are 2.44 Å. Both Fe(1)-Fe(7) bond lengths are 2.69 Å. Both Fe(1)-Si(1) bond lengths are 2.40 Å. In the second Fe site, Fe(2) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ti(1), one Fe(3), one Fe(4), one Fe(8), two equivalent Fe(5), two equivalent Fe(6), and two equivalent Si(1) atoms. The Fe(2)-Fe(3) bond length is 2.58 Å. The Fe(2)-Fe(4) bond length is 2.63 Å. The Fe(2)-Fe(8) bond length is 2.70 Å. Both Fe(2)-Fe(5) bond lengths are 2.40 Å. Both Fe(2)-Fe(6) bond lengths are 2.67 Å. Both Fe(2)-Si(1) bond lengths are 2.42 Å. In the third Fe site, Fe(3) is bonded to two equivalent Gd(1), two equivalent Ti(1), one Fe(1), one Fe(2), one Fe(6), one Fe(7), two equivalent Fe(5), and two equivalent Si(1) atoms to form distorted FeGd2Ti2Fe6Si2 cuboctahedra that share corners with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, corners with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra, corners with six equivalent Fe(4)Gd2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(4)Gd2Fe8Si2 cuboctahedra, edges with two equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, edges with two equivalent Fe(5)Gd2TiFe9 cuboctahedra, edges with two equivalent Si(1)Gd2TiFe7Si2 cuboctahedra,  a faceface with one Fe(4)Gd2Fe8Si2 cuboctahedra, faces with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, and faces with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra. The Fe(3)-Fe(6) bond length is 2.52 Å. The Fe(3)-Fe(7) bond length is 2.60 Å. Both Fe(3)-Fe(5) bond lengths are 2.42 Å. Both Fe(3)-Si(1) bond lengths are 2.43 Å. In the fourth Fe site, Fe(4) is bonded to two equivalent Gd(1), one Fe(1), one Fe(2), one Fe(6), one Fe(7), two equivalent Fe(5), two equivalent Fe(8), and two equivalent Si(1) atoms to form distorted FeGd2Fe8Si2 cuboctahedra that share corners with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, corners with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra, corners with six equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra,  an edgeedge with one Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, edges with two equivalent Fe(4)Gd2Fe8Si2 cuboctahedra, edges with two equivalent Fe(5)Gd2TiFe9 cuboctahedra, edges with two equivalent Si(1)Gd2TiFe7Si2 cuboctahedra,  a faceface with one Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, faces with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, and faces with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra. The Fe(4)-Fe(6) bond length is 2.61 Å. The Fe(4)-Fe(7) bond length is 2.53 Å. Both Fe(4)-Fe(5) bond lengths are 2.39 Å. Both Fe(4)-Fe(8) bond lengths are 2.62 Å. Both Fe(4)-Si(1) bond lengths are 2.39 Å. In the fifth Fe site, Fe(5) is bonded to two equivalent Gd(1), one Ti(1), one Fe(1), one Fe(2), one Fe(3), one Fe(4), one Fe(6), one Fe(7), one Fe(8), and two equivalent Fe(5) atoms to form distorted FeGd2TiFe9 cuboctahedra that share corners with two equivalent Fe(4)Gd2Fe8Si2 cuboctahedra, corners with two equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, corners with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra, corners with six equivalent Fe(5)Gd2TiFe9 cuboctahedra,  an edgeedge with one Fe(4)Gd2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, edges with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra, faces with two equivalent Fe(4)Gd2Fe8Si2 cuboctahedra, faces with two equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, faces with two equivalent Fe(5)Gd2TiFe9 cuboctahedra, and faces with four equivalent Si(1)Gd2TiFe7Si2 cuboctahedra. The Fe(5)-Fe(6) bond length is 2.56 Å. The Fe(5)-Fe(7) bond length is 2.58 Å. The Fe(5)-Fe(8) bond length is 2.55 Å. There is one shorter (2.39 Å) and one longer (2.42 Å) Fe(5)-Fe(5) bond length. In the sixth Fe site, Fe(6) is bonded in a 12-coordinate geometry to one Gd(1), two equivalent Ti(1), one Fe(3), one Fe(4), one Fe(7), two equivalent Fe(2), two equivalent Fe(5), and two equivalent Si(1) atoms. The Fe(6)-Fe(7) bond length is 2.38 Å. Both Fe(6)-Si(1) bond lengths are 2.55 Å. In the seventh Fe site, Fe(7) is bonded in a 14-coordinate geometry to one Gd(1), two equivalent Ti(1), one Fe(3), one Fe(4), one Fe(6), two equivalent Fe(1), two equivalent Fe(5), two equivalent Fe(8), and two equivalent Si(1) atoms. Both Fe(7)-Fe(8) bond lengths are 2.91 Å. Both Fe(7)-Si(1) bond lengths are 2.53 Å. In the eighth Fe site, Fe(8) is bonded in a 1-coordinate geometry to one Gd(1), one Ti(1), one Fe(1), one Fe(2), two equivalent Fe(4), two equivalent Fe(5), two equivalent Fe(7), and two equivalent Si(1) atoms. Both Fe(8)-Si(1) bond lengths are 2.49 Å. Si(1) is bonded to two equivalent Gd(1), one Ti(1), one Fe(1), one Fe(2), one Fe(3), one Fe(4), one Fe(6), one Fe(7), one Fe(8), and two equivalent Si(1) atoms to form distorted SiGd2TiFe7Si2 cuboctahedra that share corners with two equivalent Fe(4)Gd2Fe8Si2 cuboctahedra, corners with two equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, corners with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, corners with six equivalent Si(1)Gd2TiFe7Si2 cuboctahedra,  an edgeedge with one Fe(4)Gd2Fe8Si2 cuboctahedra,  an edgeedge with one Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, edges with four equivalent Fe(5)Gd2TiFe9 cuboctahedra, faces with two equivalent Fe(4)Gd2Fe8Si2 cuboctahedra, faces with two equivalent Fe(3)Gd2Ti2Fe6Si2 cuboctahedra, faces with two equivalent Si(1)Gd2TiFe7Si2 cuboctahedra, and faces with four equivalent Fe(5)Gd2TiFe9 cuboctahedra. There is one shorter (2.39 Å) and one longer (2.42 Å) Si(1)-Si(1) bond length.