Magnetic and superconducting transitions in Ba1-xKxFe2As2 studied by specific heat

We report on specific-heat measurements in Ba1-xKxFe2As2(x <= 0.6). For the underdoped sample with x=0.2, both the spin-density-wave transition at T=100 K and the superconducting transition at 23 K can be identified. After subtraction of the normal-state specific heat by appropriate Debye and Einstein contributions and the normal-state Sommerfeld coefficient, we can describe the electronic contribution to the specific heat in the superconducting state for concentrations 0.3 <= x <= 0.6 by a full single gap within the BCS limit.