FePt L10 (P4/mmm, #123). a=3.85 Å, c=3.71 Å, c/a=0.964. Experimental lattice parameters. For ALIGNN anchor validation — experimental Ms=1.43 T, Tc=750K, MAE~6.6 MJ/m³.
Adding a second L10 anchor resolves whether the screening chain Tc underprediction is a structural-family bias or a compound-specific anomaly.