The long-range planar-type antiferromagnetic ordering in the heavy-fermion compound ${\mathrm{CePd}}_2$${\mathrm{Al}}_3$ is shown to critically depend on the exact occupation and distribution of aluminum atoms over their available lattice sites. A poly-crystalline sample (${\mathit{T}}_{\mathit{N}}$=2.7 K) is systematically compared with a nonordering single crystal, by means of susceptibility, specific heat, and site-specific Al-NQR/NMR experiments. Implications for other Al-containing heavy-fermion systems are discussed.

• Received 30 November 1993

DOI:https://doi.org/10.1103/PhysRevB.49.15759