The superconducting phase and electronic excitations of (Rb,Cs)Fe$_{2}$As$_{2}$

We present specific heat, transport and Muon-Spin Rotation ($\mu $SR) results on (Rb,Cs)Fe$_{2}$As$_{2}$. RbFe$_{2}$As$_{2}$ was only recently found to be superconducting below 2.6 K by Bukowski et al. Compared to the related BaFe$_{2}$As$_{2}$ the electron density is lower and no magnetic order is observed. For the superconducting phase the superfluid density was calculated from $\mu $SR data. The temperature dependence of the superfluid density and the magnetic penetration depth is well described by a multi-gap scenario. In addition the electronic contribution the specific heat was studied for different compositions and magnetic fields and reveals a high value for the Sommerfeld coefficient $\gamma $.