Y4Co3Ga16 crystallizes in the tetragonal P4/mmm space group. Y(1) is bonded to two equivalent Ga(3); two equivalent Ga(4); four Ga(1,1); and four equivalent Ga(2) atoms to form YGa12 cuboctahedra that share corners with eight equivalent Y(1)Ga12 cuboctahedra, edges with two equivalent Ga(3)Y4Ga8 cuboctahedra, faces with two equivalent Ga(3)Y4Ga8 cuboctahedra, faces with five equivalent Y(1)Ga12 cuboctahedra, and faces with two equivalent Co(2)Ga6 octahedra. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a body-centered cubic geometry to eight Ga(1,1,1) atoms. In the second Co site, Co(2) is bonded to two equivalent Ga(4) and four equivalent Ga(2) atoms to form CoGa6 octahedra that share corners with eight equivalent Ga(3)Y4Ga8 cuboctahedra and faces with eight equivalent Y(1)Ga12 cuboctahedra. There are six inequivalent Ga sites. In the first Ga site, Ga(1) is bonded in a 11-coordinate geometry to two equivalent Y(1); two equivalent Co(1); one Ga(3); one Ga(4); and five Ga(1,1) atoms. In the second Ga site, Ga(1) is bonded in a 11-coordinate geometry to two equivalent Y(1); two equivalent Co(1); one Ga(3); one Ga(4); and five Ga(1,1) atoms. In the third Ga site, Ga(1) is bonded in a 11-coordinate geometry to two equivalent Y(1), two equivalent Co(1), one Ga(3), one Ga(4), and five equivalent Ga(1) atoms. In the fourth Ga site, Ga(2) is bonded in a 9-coordinate geometry to four equivalent Y(1), one Co(2), two equivalent Ga(2), and two equivalent Ga(3) atoms. In the fifth Ga site, Ga(3) is bonded to four equivalent Y(1); four Ga(1,1); and four equivalent Ga(2) atoms to form distorted GaY4Ga8 cuboctahedra that share corners with four equivalent Ga(3)Y4Ga8 cuboctahedra, corners with four equivalent Co(2)Ga6 octahedra, edges with four equivalent Y(1)Ga12 cuboctahedra,  a faceface with one Ga(3)Y4Ga8 cuboctahedra, and faces with four equivalent Y(1)Ga12 cuboctahedra. The corner-sharing octahedral tilt angles are 50°. In the sixth Ga site, Ga(4) is bonded in a 9-coordinate geometry to four equivalent Y(1); one Co(2); and four Ga(1,1) atoms.
Y4Co3Ga16 crystallizes in the tetragonal P4/mmm space group. Y(1) is bonded to two equivalent Ga(3); two equivalent Ga(4); four Ga(1,1); and four equivalent Ga(2) atoms to form YGa12 cuboctahedra that share corners with eight equivalent Y(1)Ga12 cuboctahedra, edges with two equivalent Ga(3)Y4Ga8 cuboctahedra, faces with two equivalent Ga(3)Y4Ga8 cuboctahedra, faces with five equivalent Y(1)Ga12 cuboctahedra, and faces with two equivalent Co(2)Ga6 octahedra. Both Y(1)-Ga(3) bond lengths are 3.02 Å. Both Y(1)-Ga(4) bond lengths are 3.03 Å. All Y(1)-Ga(1,1) bond lengths are 3.01 Å. All Y(1)-Ga(2) bond lengths are 3.05 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a body-centered cubic geometry to eight Ga(1,1,1) atoms. All Co(1)-Ga(1,1,1) bond lengths are 2.49 Å. In the second Co site, Co(2) is bonded to two equivalent Ga(4) and four equivalent Ga(2) atoms to form CoGa6 octahedra that share corners with eight equivalent Ga(3)Y4Ga8 cuboctahedra and faces with eight equivalent Y(1)Ga12 cuboctahedra. Both Co(2)-Ga(4) bond lengths are 2.44 Å. All Co(2)-Ga(2) bond lengths are 2.40 Å. There are six inequivalent Ga sites. In the first Ga site, Ga(1) is bonded in a 11-coordinate geometry to two equivalent Y(1); two equivalent Co(1); one Ga(3); one Ga(4); and five Ga(1,1) atoms. The Ga(1)-Ga(3) bond length is 2.98 Å. The Ga(1)-Ga(4) bond length is 2.82 Å. There are a spread of Ga(1)-Ga(1,1) bond distances ranging from 2.56-3.03 Å. In the second Ga site, Ga(1) is bonded in a 11-coordinate geometry to two equivalent Y(1); two equivalent Co(1); one Ga(3); one Ga(4); and five Ga(1,1) atoms. The Ga(1)-Ga(3) bond length is 2.98 Å. The Ga(1)-Ga(4) bond length is 2.82 Å. There are a spread of Ga(1)-Ga(1,1) bond distances ranging from 2.56-3.03 Å. In the third Ga site, Ga(1) is bonded in a 11-coordinate geometry to two equivalent Y(1), two equivalent Co(1), one Ga(3), one Ga(4), and five equivalent Ga(1) atoms. Both Ga(1)-Y(1) bond lengths are 3.01 Å. The Ga(1)-Ga(3) bond length is 2.98 Å. The Ga(1)-Ga(4) bond length is 2.82 Å. In the fourth Ga site, Ga(2) is bonded in a 9-coordinate geometry to four equivalent Y(1), one Co(2), two equivalent Ga(2), and two equivalent Ga(3) atoms. Both Ga(2)-Ga(2) bond lengths are 2.65 Å. Both Ga(2)-Ga(3) bond lengths are 2.89 Å. In the fifth Ga site, Ga(3) is bonded to four equivalent Y(1); four Ga(1,1); and four equivalent Ga(2) atoms to form distorted GaY4Ga8 cuboctahedra that share corners with four equivalent Ga(3)Y4Ga8 cuboctahedra, corners with four equivalent Co(2)Ga6 octahedra, edges with four equivalent Y(1)Ga12 cuboctahedra,  a faceface with one Ga(3)Y4Ga8 cuboctahedra, and faces with four equivalent Y(1)Ga12 cuboctahedra. The corner-sharing octahedral tilt angles are 50°. In the sixth Ga site, Ga(4) is bonded in a 9-coordinate geometry to four equivalent Y(1); one Co(2); and four Ga(1,1) atoms.