Sc3Hf2Si4 crystallizes in the tetragonal P4_12_12 space group. There are two inequivalent Sc sites. In the first Sc site, Sc(1) is bonded to two equivalent Si(1) and four equivalent Si(2) atoms to form distorted corner-sharing ScSi6 octahedra. The corner-sharing octahedral tilt angles are 54°. In the second Sc site, Sc(2) is bonded in a 7-coordinate geometry to three equivalent Si(2) and four equivalent Si(1) atoms. Hf(1) is bonded in a 6-coordinate geometry to three equivalent Si(1) and three equivalent Si(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Sc(1), four equivalent Sc(2), three equivalent Hf(1), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Sc(1), three equivalent Sc(2), three equivalent Hf(1), and one Si(1) atom.
Sc3Hf2Si4 crystallizes in the tetragonal P4_12_12 space group. There are two inequivalent Sc sites. In the first Sc site, Sc(1) is bonded to two equivalent Si(1) and four equivalent Si(2) atoms to form distorted corner-sharing ScSi6 octahedra. The corner-sharing octahedral tilt angles are 54°. Both Sc(1)-Si(1) bond lengths are 2.94 Å. There are two shorter (2.73 Å) and two longer (2.82 Å) Sc(1)-Si(2) bond lengths. In the second Sc site, Sc(2) is bonded in a 7-coordinate geometry to three equivalent Si(2) and four equivalent Si(1) atoms. There are two shorter (2.86 Å) and one longer (3.06 Å) Sc(2)-Si(2) bond length. There are a spread of Sc(2)-Si(1) bond distances ranging from 2.76-3.08 Å. Hf(1) is bonded in a 6-coordinate geometry to three equivalent Si(1) and three equivalent Si(2) atoms. There are a spread of Hf(1)-Si(1) bond distances ranging from 2.63-2.81 Å. There is one shorter (2.68 Å) and two longer (2.73 Å) Hf(1)-Si(2) bond lengths. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Sc(1), four equivalent Sc(2), three equivalent Hf(1), and one Si(2) atom. The Si(1)-Si(2) bond length is 2.51 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Sc(1), three equivalent Sc(2), three equivalent Hf(1), and one Si(1) atom.