L1_0 tau-MnAl 4x4x2 supercell (64 atoms), 1 Cu substituted on an Al site (~1.56 at.% Cu, approximating the Ramirez/Echeverri Heliyon e42952 Al-site series x=2.0-2.5). Built from validated tau_MnAl_pure_4x4x2 (P4/mmm parent, min contact 2.666 A); ordered occupancies.