Nd5Si4 crystallizes in the tetragonal P4_12_12 space group. There are three inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 6-coordinate geometry to three equivalent Si(1) and three equivalent Si(2) atoms. In the second Nd site, Nd(2) is bonded to three equivalent Si(1) and three equivalent Si(2) atoms to form a mixture of distorted face, corner, and edge-sharing NdSi6 octahedra. The corner-sharing octahedral tilt angles range from 40-47°. In the third Nd site, Nd(3) is bonded to two equivalent Si(2) and four equivalent Si(1) atoms to form a mixture of face and corner-sharing NdSi6 octahedra. The corner-sharing octahedral tilt angles range from 42-57°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Nd(3), three equivalent Nd(1), three equivalent Nd(2), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Nd(3), three equivalent Nd(1), three equivalent Nd(2), and one Si(1) atom.
Nd5Si4 crystallizes in the tetragonal P4_12_12 space group. There are three inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 6-coordinate geometry to three equivalent Si(1) and three equivalent Si(2) atoms. There are a spread of Nd(1)-Si(1) bond distances ranging from 3.08-3.12 Å. There are a spread of Nd(1)-Si(2) bond distances ranging from 2.97-3.08 Å. In the second Nd site, Nd(2) is bonded to three equivalent Si(1) and three equivalent Si(2) atoms to form a mixture of distorted face, corner, and edge-sharing NdSi6 octahedra. The corner-sharing octahedral tilt angles range from 40-47°. There are a spread of Nd(2)-Si(1) bond distances ranging from 3.16-3.35 Å. There are a spread of Nd(2)-Si(2) bond distances ranging from 3.15-3.27 Å. In the third Nd site, Nd(3) is bonded to two equivalent Si(2) and four equivalent Si(1) atoms to form a mixture of face and corner-sharing NdSi6 octahedra. The corner-sharing octahedral tilt angles range from 42-57°. Both Nd(3)-Si(2) bond lengths are 3.15 Å. There are two shorter (3.12 Å) and two longer (3.19 Å) Nd(3)-Si(1) bond lengths. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Nd(3), three equivalent Nd(1), three equivalent Nd(2), and one Si(2) atom. The Si(1)-Si(2) bond length is 2.45 Å. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to one Nd(3), three equivalent Nd(1), three equivalent Nd(2), and one Si(1) atom.