Exotic superconducting state embedded in the hidden order of URu₂ Si₂

Using ultraclean single crystals, a number of unprecedented superconducting properties are reported in heavy-Fermion compound URu₂ Si₂. The uniqueness is best highlighted by the field-induced superconductor-insulator-like first-order transition at upper critical fields, which is a direct consequence of the electronic structure imposed by the "hidden order". There is also strong evidence for two distinct superconducting gaps having different nodal topology. This intriguing superconducting state adds a unique and exciting example to the list of unconventional superconductors.