Yb3Tm 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 Tm(1) atoms to form YbYb8Tm4 cuboctahedra that share corners with four equivalent Tm(1)Yb12 cuboctahedra, corners with fourteen equivalent Yb(1)Yb8Tm4 cuboctahedra, edges with six equivalent Tm(1)Yb12 cuboctahedra, edges with twelve equivalent Yb(1)Yb8Tm4 cuboctahedra, faces with four equivalent Tm(1)Yb12 cuboctahedra, and faces with sixteen equivalent Yb(1)Yb8Tm4 cuboctahedra. Tm(1) is bonded to twelve equivalent Yb(1) atoms to form TmYb12 cuboctahedra that share corners with six equivalent Tm(1)Yb12 cuboctahedra, corners with twelve equivalent Yb(1)Yb8Tm4 cuboctahedra, edges with eighteen equivalent Yb(1)Yb8Tm4 cuboctahedra, faces with eight equivalent Tm(1)Yb12 cuboctahedra, and faces with twelve equivalent Yb(1)Yb8Tm4 cuboctahedra.
Yb3Tm 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 Tm(1) atoms to form YbYb8Tm4 cuboctahedra that share corners with four equivalent Tm(1)Yb12 cuboctahedra, corners with fourteen equivalent Yb(1)Yb8Tm4 cuboctahedra, edges with six equivalent Tm(1)Yb12 cuboctahedra, edges with twelve equivalent Yb(1)Yb8Tm4 cuboctahedra, faces with four equivalent Tm(1)Yb12 cuboctahedra, and faces with sixteen equivalent Yb(1)Yb8Tm4 cuboctahedra. There are a spread of Yb(1)-Yb(1) bond distances ranging from 3.65-3.84 Å. There are two shorter (3.69 Å) and two longer (3.75 Å) Yb(1)-Tm(1) bond lengths. Tm(1) is bonded to twelve equivalent Yb(1) atoms to form TmYb12 cuboctahedra that share corners with six equivalent Tm(1)Yb12 cuboctahedra, corners with twelve equivalent Yb(1)Yb8Tm4 cuboctahedra, edges with eighteen equivalent Yb(1)Yb8Tm4 cuboctahedra, faces with eight equivalent Tm(1)Yb12 cuboctahedra, and faces with twelve equivalent Yb(1)Yb8Tm4 cuboctahedra.