Detecting Hidden Altermagnetism Under A Fixed Sign Contract: CD-RPED As A Sublattice-Resolved Probe

Significant — This significant manuscript, Detecting Hidden Altermagnetism Under A Fixed Sign Contract: CD-RPED As A Sublattice-Resolved Probe, converts the “hidden magnetism” claim for altermagnets into a replayable, falsifier-first decision object by (i) treating scalar/net-moment cancellation as permitted while (ii) requiring a pattern-valued, swap-consistent sign record (helicity reversal, sublattice labeling swap, and Neel-axis alignment gate) to survive tightening under tokens-only replay; the core deliverable is a portable certification template that separates recognition from enforcement (SEB→MAP), logs a minimal ledger row (contract_id, corridor_id, pad_id, window_hash, helicity_swap, sublattice_swap, neel_align, sign_triad, zeros_count, stlf_flag, sw_grade, map_action), and enforces a tightening ladder with explicit falsifiers (off-resonance collapse, misalignment collapse, domain-causal response, disable-L nulls, and leave-one-out 4S3 audit) so that success cannot be achieved by window shopping, postselection, or analysis repair; the result is a raised-bar path for thin-film/surface altermagnet readout where “hidden” stops meaning interpretive and becomes an accept/downgrade/refuse outcome that can be replayed and audited.