Hidden Magnetism Made Operational: CD-RPED and RIXS Under a Fixed Sign Contract

This manuscript builds directly on the article "Sign-First Unification in Magnetic Readout: Certified Streets Across Chiral, Altermagnetic, Anti-, And Ferro-Magnets Under a Shared P-Lane Contract" by taking the unified contract language and applying it to “hidden magnetism” in altermagnets, where conventional magnetometry can fail while transport and dichroic probes still carry directional information; it operationalizes altermagnet readout as a three-bench lane (write, probe, transport) with a signed-triad certificate (alternating patterns −+− and +−+) under declared swaps, and it makes the fragile parts explicit (freeze vs no-freeze, directive handoff, zeros accounting), so the claim becomes “a signed pattern survives a fixed contract” rather than “a single sensor is persuasive.