H1 Mn-Al-C GGen exploration candidate (action 01a06e15-0cb2-702f-bc28-fec045530a28, e_above_hull 62 meV/atom). Validated 2026-09-04: parsed, reduced formula Mn13Al3C2, 18 sites, SG Pmm2 (25) (symprec 0.01 and 0.1), density 6.75 g/cm3, min pair distance 1.87 A, ordered.