Specific heat jump at superconducting transition in the presence of Spin-Density-Wave in iron-pnictides

We analyze the magnitude of the specific heat jump ∆C at the superconducting transition temperature Tc in the situation when superconductivity develops in the pre-existing antiferromagnetic phase. We show that ∆C/Tc differs from the BCS value and is peaked at the tri-critical point where this coexistence phase first emerges. Deeper in the magnetic phase, the onset of coexistence, Tc, drops and ∆C/Tc decreases, roughly as ∆C/Tc ∝ T 2 c at intermediate Tc and exponentially at the lowest Tc, in agreement with the observed behavior of ∆C/Tc in iron-based superconductors.