YCo4Al crystallizes in the hexagonal P-6m2 space group. Y(1) is bonded in a 18-coordinate geometry to three equivalent Co(1), twelve equivalent Co(2), and three equivalent Al(1) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to three equivalent Y(1), six equivalent Co(2), and three equivalent Al(1) atoms to form CoY3Al3Co6 cuboctahedra that share corners with nine equivalent Al(1)Y3Co9 cuboctahedra, corners with twelve equivalent Co(2)Y4Al2Co6 cuboctahedra, edges with six equivalent Co(1)Y3Al3Co6 cuboctahedra, faces with two equivalent Co(1)Y3Al3Co6 cuboctahedra, faces with three equivalent Al(1)Y3Co9 cuboctahedra, and faces with eighteen equivalent Co(2)Y4Al2Co6 cuboctahedra. In the second Co site, Co(2) is bonded to four equivalent Y(1), two equivalent Co(1), four equivalent Co(2), and two equivalent Al(1) atoms to form distorted CoY4Al2Co6 cuboctahedra that share corners with four equivalent Co(1)Y3Al3Co6 cuboctahedra, corners with four equivalent Al(1)Y3Co9 cuboctahedra, corners with sixteen equivalent Co(2)Y4Al2Co6 cuboctahedra, edges with ten equivalent Co(2)Y4Al2Co6 cuboctahedra, faces with six equivalent Co(1)Y3Al3Co6 cuboctahedra, faces with six equivalent Al(1)Y3Co9 cuboctahedra, and faces with ten equivalent Co(2)Y4Al2Co6 cuboctahedra. Al(1) is bonded to three equivalent Y(1), three equivalent Co(1), and six equivalent Co(2) atoms to form distorted AlY3Co9 cuboctahedra that share corners with nine equivalent Co(1)Y3Al3Co6 cuboctahedra, corners with twelve equivalent Co(2)Y4Al2Co6 cuboctahedra, edges with six equivalent Al(1)Y3Co9 cuboctahedra, faces with two equivalent Al(1)Y3Co9 cuboctahedra, faces with three equivalent Co(1)Y3Al3Co6 cuboctahedra, and faces with eighteen equivalent Co(2)Y4Al2Co6 cuboctahedra.
YCo4Al crystallizes in the hexagonal P-6m2 space group. Y(1) is bonded in a 18-coordinate geometry to three equivalent Co(1), twelve equivalent Co(2), and three equivalent Al(1) atoms. All Y(1)-Co(1) bond lengths are 2.91 Å. All Y(1)-Co(2) bond lengths are 3.18 Å. All Y(1)-Al(1) bond lengths are 2.91 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to three equivalent Y(1), six equivalent Co(2), and three equivalent Al(1) atoms to form CoY3Al3Co6 cuboctahedra that share corners with nine equivalent Al(1)Y3Co9 cuboctahedra, corners with twelve equivalent Co(2)Y4Al2Co6 cuboctahedra, edges with six equivalent Co(1)Y3Al3Co6 cuboctahedra, faces with two equivalent Co(1)Y3Al3Co6 cuboctahedra, faces with three equivalent Al(1)Y3Co9 cuboctahedra, and faces with eighteen equivalent Co(2)Y4Al2Co6 cuboctahedra. All Co(1)-Co(2) bond lengths are 2.40 Å. All Co(1)-Al(1) bond lengths are 2.91 Å. In the second Co site, Co(2) is bonded to four equivalent Y(1), two equivalent Co(1), four equivalent Co(2), and two equivalent Al(1) atoms to form distorted CoY4Al2Co6 cuboctahedra that share corners with four equivalent Co(1)Y3Al3Co6 cuboctahedra, corners with four equivalent Al(1)Y3Co9 cuboctahedra, corners with sixteen equivalent Co(2)Y4Al2Co6 cuboctahedra, edges with ten equivalent Co(2)Y4Al2Co6 cuboctahedra, faces with six equivalent Co(1)Y3Al3Co6 cuboctahedra, faces with six equivalent Al(1)Y3Co9 cuboctahedra, and faces with ten equivalent Co(2)Y4Al2Co6 cuboctahedra. There are two shorter (2.47 Å) and two longer (2.57 Å) Co(2)-Co(2) bond lengths. Both Co(2)-Al(1) bond lengths are 2.44 Å. Al(1) is bonded to three equivalent Y(1), three equivalent Co(1), and six equivalent Co(2) atoms to form distorted AlY3Co9 cuboctahedra that share corners with nine equivalent Co(1)Y3Al3Co6 cuboctahedra, corners with twelve equivalent Co(2)Y4Al2Co6 cuboctahedra, edges with six equivalent Al(1)Y3Co9 cuboctahedra, faces with two equivalent Al(1)Y3Co9 cuboctahedra, faces with three equivalent Co(1)Y3Al3Co6 cuboctahedra, and faces with eighteen equivalent Co(2)Y4Al2Co6 cuboctahedra.