Electronic behavior of superconducting SmFeAsO0.75

High-quality polycrystalline SmFeAsO0.75 was synthesized with a superconducting transition width less than 1 K, and the electronic behavior was systematically studied by transport and specific heat measurements. An obvious superconducting jump was witnessed, together with a very small normalized superconducting jump, ΔC/γnTc ∼ 0.2, which is much smaller than expected from the BCS theory. A strong temperature-dependent Hall coefficient was found and attributed to the partial gapping of the Fermi surface up to the temperature of 160 K, which was predicted and supported by the emergence of the pseudogap. The charge-carrier density as well as the effective mass were also obtained and discussed in detail.