La2RhSi3 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent La sites. In the first La site, La(1) is bonded to twelve equivalent Si(1) atoms to form LaSi12 cuboctahedra that share edges with twelve equivalent La(2)Si8Rh4 cuboctahedra, faces with two equivalent La(1)Si12 cuboctahedra, and faces with six equivalent La(2)Si8Rh4 cuboctahedra. In the second La site, La(2) is bonded to four equivalent Rh(1) and eight equivalent Si(1) atoms to form LaSi8Rh4 cuboctahedra that share edges with four equivalent La(1)Si12 cuboctahedra, edges with eight equivalent La(2)Si8Rh4 cuboctahedra, faces with two equivalent La(1)Si12 cuboctahedra, and faces with six equivalent La(2)Si8Rh4 cuboctahedra. Rh(1) is bonded in a 9-coordinate geometry to six equivalent La(2) and three equivalent Si(1) atoms. Si(1) is bonded in a 9-coordinate geometry to two equivalent La(1), four equivalent La(2), one Rh(1), and two equivalent Si(1) atoms.
La2RhSi3 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent La sites. In the first La site, La(1) is bonded to twelve equivalent Si(1) atoms to form LaSi12 cuboctahedra that share edges with twelve equivalent La(2)Si8Rh4 cuboctahedra, faces with two equivalent La(1)Si12 cuboctahedra, and faces with six equivalent La(2)Si8Rh4 cuboctahedra. There are six shorter (3.21 Å) and six longer (3.23 Å) La(1)-Si(1) bond lengths. In the second La site, La(2) is bonded to four equivalent Rh(1) and eight equivalent Si(1) atoms to form LaSi8Rh4 cuboctahedra that share edges with four equivalent La(1)Si12 cuboctahedra, edges with eight equivalent La(2)Si8Rh4 cuboctahedra, faces with two equivalent La(1)Si12 cuboctahedra, and faces with six equivalent La(2)Si8Rh4 cuboctahedra. There are two shorter (3.21 Å) and two longer (3.24 Å) La(2)-Rh(1) bond lengths. There are four shorter (3.22 Å) and four longer (3.25 Å) La(2)-Si(1) bond lengths. Rh(1) is bonded in a 9-coordinate geometry to six equivalent La(2) and three equivalent Si(1) atoms. All Rh(1)-Si(1) bond lengths are 2.42 Å. Si(1) is bonded in a 9-coordinate geometry to two equivalent La(1), four equivalent La(2), one Rh(1), and two equivalent Si(1) atoms. Both Si(1)-Si(1) bond lengths are 2.40 Å.