Yb3Er is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Yb(1) is bonded to eight equivalent Yb(1) and four equivalent Er(1) atoms to form YbYb8Er4 cuboctahedra that share corners with four equivalent Er(1)Yb12 cuboctahedra, corners with fourteen equivalent Yb(1)Yb8Er4 cuboctahedra, edges with six equivalent Er(1)Yb12 cuboctahedra, edges with twelve equivalent Yb(1)Yb8Er4 cuboctahedra, faces with four equivalent Er(1)Yb12 cuboctahedra, and faces with sixteen equivalent Yb(1)Yb8Er4 cuboctahedra. Er(1) is bonded to twelve equivalent Yb(1) atoms to form ErYb12 cuboctahedra that share corners with six equivalent Er(1)Yb12 cuboctahedra, corners with twelve equivalent Yb(1)Yb8Er4 cuboctahedra, edges with eighteen equivalent Yb(1)Yb8Er4 cuboctahedra, faces with eight equivalent Er(1)Yb12 cuboctahedra, and faces with twelve equivalent Yb(1)Yb8Er4 cuboctahedra.
Yb3Er is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Yb(1) is bonded to eight equivalent Yb(1) and four equivalent Er(1) atoms to form YbYb8Er4 cuboctahedra that share corners with four equivalent Er(1)Yb12 cuboctahedra, corners with fourteen equivalent Yb(1)Yb8Er4 cuboctahedra, edges with six equivalent Er(1)Yb12 cuboctahedra, edges with twelve equivalent Yb(1)Yb8Er4 cuboctahedra, faces with four equivalent Er(1)Yb12 cuboctahedra, and faces with sixteen equivalent Yb(1)Yb8Er4 cuboctahedra. There are a spread of Yb(1)-Yb(1) bond distances ranging from 3.65-3.83 Å. There are two shorter (3.69 Å) and two longer (3.74 Å) Yb(1)-Er(1) bond lengths. Er(1) is bonded to twelve equivalent Yb(1) atoms to form ErYb12 cuboctahedra that share corners with six equivalent Er(1)Yb12 cuboctahedra, corners with twelve equivalent Yb(1)Yb8Er4 cuboctahedra, edges with eighteen equivalent Yb(1)Yb8Er4 cuboctahedra, faces with eight equivalent Er(1)Yb12 cuboctahedra, and faces with twelve equivalent Yb(1)Yb8Er4 cuboctahedra.