CeIrIn5 is a member of a new family of heavy-fermion compounds and has a Sommerfeld specific-heat coefficient of 720 mJ/molK2. It exhibits a bulk, thermodynamic transition to a superconducting state at Tc = 0.40 K, below which the specific heat decreases as T2 to a small residual T-linear value. Surprisingly, the electrical resistivity drops below instrumental resolution at a much higher temperature T0 = 1.2 K. These behaviors are highly reproducible and field-dependent studies indicate that T0 and Tc arise from the same underlying electronic structure. The layered crystal structure of CeIrIn5 suggests a possible analogy to the cuprates in which spin/charge pair correlations develop well above Tc.

A new heavy-fermion superconductor CeIrIn 5 : A relative of the cuprates?