ErMoC2 crystallizes in the orthorhombic Pnma space group. Er(1) is bonded to three equivalent C(2) and four equivalent C(1) atoms to form distorted ErC7 pentagonal bipyramids that share corners with four equivalent Er(1)C7 pentagonal bipyramids, corners with three equivalent Mo(1)C5 trigonal bipyramids, edges with four equivalent Er(1)C7 pentagonal bipyramids, edges with seven equivalent Mo(1)C5 trigonal bipyramids, and faces with two equivalent Er(1)C7 pentagonal bipyramids. Mo(1) is bonded to two equivalent C(1) and three equivalent C(2) atoms to form MoC5 trigonal bipyramids that share corners with three equivalent Er(1)C7 pentagonal bipyramids, corners with four equivalent Mo(1)C5 trigonal bipyramids, edges with seven equivalent Er(1)C7 pentagonal bipyramids, and edges with two equivalent Mo(1)C5 trigonal bipyramids. There are two inequivalent C sites. In the first C site, C(1) is bonded to four equivalent Er(1) and two equivalent Mo(1) atoms to form CEr4Mo2 octahedra that share corners with four equivalent C(1)Er4Mo2 octahedra, corners with nine equivalent C(2)Er3Mo3 octahedra, edges with two equivalent C(1)Er4Mo2 octahedra, edges with three equivalent C(2)Er3Mo3 octahedra,  a faceface with one C(2)Er3Mo3 octahedra, and faces with two equivalent C(1)Er4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 12-60°. In the second C site, C(2) is bonded to three equivalent Er(1) and three equivalent Mo(1) atoms to form CEr3Mo3 octahedra that share corners with nine equivalent C(1)Er4Mo2 octahedra, edges with three equivalent C(1)Er4Mo2 octahedra, edges with six equivalent C(2)Er3Mo3 octahedra, and  a faceface with one C(1)Er4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 12-60°.
ErMoC2 crystallizes in the orthorhombic Pnma space group. Er(1) is bonded to three equivalent C(2) and four equivalent C(1) atoms to form distorted ErC7 pentagonal bipyramids that share corners with four equivalent Er(1)C7 pentagonal bipyramids, corners with three equivalent Mo(1)C5 trigonal bipyramids, edges with four equivalent Er(1)C7 pentagonal bipyramids, edges with seven equivalent Mo(1)C5 trigonal bipyramids, and faces with two equivalent Er(1)C7 pentagonal bipyramids. There is one shorter (2.43 Å) and two longer (2.57 Å) Er(1)-C(2) bond lengths. There are two shorter (2.48 Å) and two longer (2.55 Å) Er(1)-C(1) bond lengths. Mo(1) is bonded to two equivalent C(1) and three equivalent C(2) atoms to form MoC5 trigonal bipyramids that share corners with three equivalent Er(1)C7 pentagonal bipyramids, corners with four equivalent Mo(1)C5 trigonal bipyramids, edges with seven equivalent Er(1)C7 pentagonal bipyramids, and edges with two equivalent Mo(1)C5 trigonal bipyramids. There is one shorter (2.02 Å) and one longer (2.13 Å) Mo(1)-C(1) bond length. There are two shorter (2.10 Å) and one longer (2.28 Å) Mo(1)-C(2) bond length. There are two inequivalent C sites. In the first C site, C(1) is bonded to four equivalent Er(1) and two equivalent Mo(1) atoms to form CEr4Mo2 octahedra that share corners with four equivalent C(1)Er4Mo2 octahedra, corners with nine equivalent C(2)Er3Mo3 octahedra, edges with two equivalent C(1)Er4Mo2 octahedra, edges with three equivalent C(2)Er3Mo3 octahedra,  a faceface with one C(2)Er3Mo3 octahedra, and faces with two equivalent C(1)Er4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 12-60°. In the second C site, C(2) is bonded to three equivalent Er(1) and three equivalent Mo(1) atoms to form CEr3Mo3 octahedra that share corners with nine equivalent C(1)Er4Mo2 octahedra, edges with three equivalent C(1)Er4Mo2 octahedra, edges with six equivalent C(2)Er3Mo3 octahedra, and  a faceface with one C(1)Er4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 12-60°.