A gentle reconstruction Changes in the volume of a material’s Fermi surface are typically associated with the breaking of symmetry. Maksimovic et al . found evidence for an unusual type of this Fermi surface reconstruction, one without symmetry breaking, in the heavy fermion compound cerium cobalt indium (CeCoIn ₅ ). Doping the material with tin led to abrupt changes in Hall effect, quantum oscillation, and photoemission signals. The researchers interpret the findings in terms of the delocalization of f-electrons associated with cerium atoms. —JS