Mn20Ge13 exchange couplings (Jij)

Smaller-cell requeue for the C3/C6(b) TB2J ordering test (verification receipts dataset 019fde0f): 1x1x2 ordered supercell of the Zhang et al. 2026 (arXiv:2607.21891) high-pressure Mn5Ge3+x model (paper Fig. S3 cell a=7.273 A, c=5.36 A, excess Ge at the P63/mcm 2a interstitial). Sliced from the validated 82-atom 1x1x5 model (file:cca186b2-c496-436b-8e4e-cce40767fc84); composition Mn20Ge13 = Mn5Ge3.25, min pair 2.206 A, symmetry P-31m robust at symprec 0.01-0.1. Built to fit the 45-min stale-action reaper that reaped three 82-atom attempts.