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The zero Hall plateau alone does not discriminate. An answer is an identification from a surface-resolved or theta-sensitive measurement.","problem_ref":null,"references":"","settled_by":"Layer-resolved Kerr or Faraday rotation, nonlocal transport, or a magnetoelectric measurement isolating the $\\theta = \\pi$ response.","status_note":"","title":"Is even-layer MnBi2Te4 an axion 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