LaCo5H3 crystallizes in the monoclinic P2/m space group. La(1) is bonded in a 8-coordinate geometry to two equivalent Co(2), two equivalent H(1), and four equivalent H(2) atoms. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 8-coordinate geometry to two equivalent Co(3), two equivalent Co(4), and four equivalent Co(2) atoms. In the second Co site, Co(2) is bonded in a distorted single-bond geometry to one La(1), two equivalent Co(1), and one H(1) atom. In the third Co site, Co(3) is bonded in a linear geometry to two equivalent Co(1) and two equivalent H(2) atoms. In the fourth Co site, Co(4) is bonded in a distorted square co-planar geometry to two equivalent Co(1), two equivalent H(1), and two equivalent H(2) atoms. There are two inequivalent H sites. In the first H site, H(1) is bonded to two equivalent La(1), two equivalent Co(2), and two equivalent Co(4) atoms to form HLa2Co4 octahedra that share corners with four equivalent H(1)La2Co4 octahedra, corners with four equivalent H(2)La2Co2 tetrahedra, and edges with four equivalent H(2)La2Co2 tetrahedra. The corner-sharing octahedra are not tilted. In the second H site, H(2) is bonded to two equivalent La(1), one Co(3), and one Co(4) atom to form HLa2Co2 tetrahedra that share corners with two equivalent H(1)La2Co4 octahedra, corners with six equivalent H(2)La2Co2 tetrahedra, edges with two equivalent H(1)La2Co4 octahedra, and  an edgeedge with one H(2)La2Co2 tetrahedra. The corner-sharing octahedral tilt angles are 63°.
LaCo5H3 crystallizes in the monoclinic P2/m space group. La(1) is bonded in a 8-coordinate geometry to two equivalent Co(2), two equivalent H(1), and four equivalent H(2) atoms. Both La(1)-Co(2) bond lengths are 2.87 Å. Both La(1)-H(1) bond lengths are 2.52 Å. All La(1)-H(2) bond lengths are 2.39 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 8-coordinate geometry to two equivalent Co(3), two equivalent Co(4), and four equivalent Co(2) atoms. Both Co(1)-Co(3) bond lengths are 2.52 Å. Both Co(1)-Co(4) bond lengths are 2.62 Å. All Co(1)-Co(2) bond lengths are 2.38 Å. In the second Co site, Co(2) is bonded in a distorted single-bond geometry to one La(1), two equivalent Co(1), and one H(1) atom. The Co(2)-H(1) bond length is 1.75 Å. In the third Co site, Co(3) is bonded in a linear geometry to two equivalent Co(1) and two equivalent H(2) atoms. Both Co(3)-H(2) bond lengths are 1.63 Å. In the fourth Co site, Co(4) is bonded in a distorted square co-planar geometry to two equivalent Co(1), two equivalent H(1), and two equivalent H(2) atoms. Both Co(4)-H(1) bond lengths are 2.02 Å. Both Co(4)-H(2) bond lengths are 1.60 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded to two equivalent La(1), two equivalent Co(2), and two equivalent Co(4) atoms to form HLa2Co4 octahedra that share corners with four equivalent H(1)La2Co4 octahedra, corners with four equivalent H(2)La2Co2 tetrahedra, and edges with four equivalent H(2)La2Co2 tetrahedra. The corner-sharing octahedra are not tilted. In the second H site, H(2) is bonded to two equivalent La(1), one Co(3), and one Co(4) atom to form HLa2Co2 tetrahedra that share corners with two equivalent H(1)La2Co4 octahedra, corners with six equivalent H(2)La2Co2 tetrahedra, edges with two equivalent H(1)La2Co4 octahedra, and  an edgeedge with one H(2)La2Co2 tetrahedra. The corner-sharing octahedral tilt angles are 63°.