Figure 1 Projection of the crystal structures of Al4C3 (Gesing & Jeitschko, 1995) (left) showing the fivefold coordination of C (brown) in –Al2C2– blocks between the –Al2C– blocks with C in sixfold coordination to Al (blue) atoms; Al5C3N (right) as reported by Jeffrey & Wu (1963) with additional –AlN– layers (gray tetrahedra).