TmNi3 crystallizes in the trigonal R-3m space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 12-coordinate geometry to three equivalent Ni(3) and nine equivalent Ni(1) atoms. In the second Tm site, Tm(2) is bonded in a distorted hexagonal planar geometry to six equivalent Ni(2) and twelve equivalent Ni(1) atoms. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent Tm(2), three equivalent Tm(1), one Ni(3), two equivalent Ni(2), and four equivalent Ni(1) atoms to form distorted NiTm5Ni7 cuboctahedra that share corners with two equivalent Ni(3)Tm6Ni6 cuboctahedra, corners with fifteen equivalent Ni(1)Tm5Ni7 cuboctahedra, edges with eight equivalent Ni(1)Tm5Ni7 cuboctahedra, faces with three equivalent Ni(3)Tm6Ni6 cuboctahedra, and faces with eleven equivalent Ni(1)Tm5Ni7 cuboctahedra. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to three equivalent Tm(2) and six equivalent Ni(1) atoms. In the third Ni site, Ni(3) is bonded to six equivalent Tm(1) and six equivalent Ni(1) atoms to form NiTm6Ni6 cuboctahedra that share corners with twelve equivalent Ni(1)Tm5Ni7 cuboctahedra, edges with six equivalent Ni(3)Tm6Ni6 cuboctahedra, and faces with eighteen equivalent Ni(1)Tm5Ni7 cuboctahedra.
TmNi3 crystallizes in the trigonal R-3m space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded in a 12-coordinate geometry to three equivalent Ni(3) and nine equivalent Ni(1) atoms. All Tm(1)-Ni(3) bond lengths are 2.89 Å. There are six shorter (2.79 Å) and three longer (3.03 Å) Tm(1)-Ni(1) bond lengths. In the second Tm site, Tm(2) is bonded in a distorted hexagonal planar geometry to six equivalent Ni(2) and twelve equivalent Ni(1) atoms. All Tm(2)-Ni(2) bond lengths are 2.82 Å. All Tm(2)-Ni(1) bond lengths are 3.13 Å. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent Tm(2), three equivalent Tm(1), one Ni(3), two equivalent Ni(2), and four equivalent Ni(1) atoms to form distorted NiTm5Ni7 cuboctahedra that share corners with two equivalent Ni(3)Tm6Ni6 cuboctahedra, corners with fifteen equivalent Ni(1)Tm5Ni7 cuboctahedra, edges with eight equivalent Ni(1)Tm5Ni7 cuboctahedra, faces with three equivalent Ni(3)Tm6Ni6 cuboctahedra, and faces with eleven equivalent Ni(1)Tm5Ni7 cuboctahedra. The Ni(1)-Ni(3) bond length is 2.47 Å. There is one shorter (2.40 Å) and one longer (2.42 Å) Ni(1)-Ni(2) bond length. There are two shorter (2.43 Å) and two longer (2.45 Å) Ni(1)-Ni(1) bond lengths. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to three equivalent Tm(2) and six equivalent Ni(1) atoms. In the third Ni site, Ni(3) is bonded to six equivalent Tm(1) and six equivalent Ni(1) atoms to form NiTm6Ni6 cuboctahedra that share corners with twelve equivalent Ni(1)Tm5Ni7 cuboctahedra, edges with six equivalent Ni(3)Tm6Ni6 cuboctahedra, and faces with eighteen equivalent Ni(1)Tm5Ni7 cuboctahedra.