ErSm3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Er(1) is bonded to twelve equivalent Sm(1) atoms to form ErSm12 cuboctahedra that share corners with six equivalent Er(1)Sm12 cuboctahedra, corners with twelve equivalent Sm(1)Sm8Er4 cuboctahedra, edges with eighteen equivalent Sm(1)Sm8Er4 cuboctahedra, faces with eight equivalent Er(1)Sm12 cuboctahedra, and faces with twelve equivalent Sm(1)Sm8Er4 cuboctahedra. Sm(1) is bonded to four equivalent Er(1) and eight equivalent Sm(1) atoms to form SmSm8Er4 cuboctahedra that share corners with four equivalent Er(1)Sm12 cuboctahedra, corners with fourteen equivalent Sm(1)Sm8Er4 cuboctahedra, edges with six equivalent Er(1)Sm12 cuboctahedra, edges with twelve equivalent Sm(1)Sm8Er4 cuboctahedra, faces with four equivalent Er(1)Sm12 cuboctahedra, and faces with sixteen equivalent Sm(1)Sm8Er4 cuboctahedra.
ErSm3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Er(1) is bonded to twelve equivalent Sm(1) atoms to form ErSm12 cuboctahedra that share corners with six equivalent Er(1)Sm12 cuboctahedra, corners with twelve equivalent Sm(1)Sm8Er4 cuboctahedra, edges with eighteen equivalent Sm(1)Sm8Er4 cuboctahedra, faces with eight equivalent Er(1)Sm12 cuboctahedra, and faces with twelve equivalent Sm(1)Sm8Er4 cuboctahedra. There are six shorter (3.59 Å) and six longer (3.67 Å) Er(1)-Sm(1) bond lengths. Sm(1) is bonded to four equivalent Er(1) and eight equivalent Sm(1) atoms to form SmSm8Er4 cuboctahedra that share corners with four equivalent Er(1)Sm12 cuboctahedra, corners with fourteen equivalent Sm(1)Sm8Er4 cuboctahedra, edges with six equivalent Er(1)Sm12 cuboctahedra, edges with twelve equivalent Sm(1)Sm8Er4 cuboctahedra, faces with four equivalent Er(1)Sm12 cuboctahedra, and faces with sixteen equivalent Sm(1)Sm8Er4 cuboctahedra. There are a spread of Sm(1)-Sm(1) bond distances ranging from 3.61-3.72 Å.