(SnS)₁.₁₅(TaS₂) is a misfit layered compound — alternating sheets of tin sulfide and tantalum disulfide that don't share the same periodicity. It superconducts at ambient pressure. Squeeze it to 14.7 GPa and the superconductivity disappears. Keep squeezing. At 80 GPa, it superconducts again, and stays superconducting to at least 150 GPa.
Reentrant superconductivity is not new. But what makes this case unusual, as reported by the team behind arXiv 2602.22999 (February 2026), is the absence of structural change. X-ray diffraction shows no phase transition anywhere in the 0–150 GPa range. The crystal lattice compresses smoothly. Nothing breaks, nothing reorganizes, nothing transforms. The atoms stay in the same arrangement.
What changes is the electronic structure. Around 60 GPa — deep in the non-superconducting window — the Hall coefficient reverses sign. The charge carriers that conduct electricity switch from one type to another (electron-like to hole-like, or the reverse). The normal-state resistance evolves nonmonotonically, rising and falling with pressure in a way that tracks an electronic reconstruction rather than a lattice transformation. The Fermi surface is being rebuilt under pressure, not the crystal.
So the superconductivity that returns at 80 GPa is not the superconductivity that disappeared at 14.7 GPa. The carrier type is different. The pairing mechanism, insofar as it depends on Fermi surface geometry, is different. The Tc trends differently with pressure. By every electronic measure, it's a new superconducting state — housed in the same crystal, expressed through the same resistance drop, but arising from a different electronic identity.
The crystal doesn't know the difference. It just provides the lattice. The electrons rebuild their collective behavior twice — once suppressed, once reborn — and the property looks the same from the outside. One resistance measurement wouldn't tell you there were two distinct superconductors in there. You need the Hall data, the pressure dependence, the normal-state resistance trajectory to see that the thing that returned is not the thing that left.
Same house. Different occupant. Same behavior.