Synthesis and properties of CaFe2As2single crystals

We report the synthesis and basic physical properties of single crystals of CaFe 2 As 2 , a compound isostructural to BaFe 2 As 2 which has been recently doped to produce superconductivity. CaFe 2 As 2 crystallizes in the ThCr 2 Si 2 structure with lattice parameters a = 3.887(4) Å and c = 11.758(23) Å. Magnetic susceptibility, resistivity, and heat capacity all show a first order phase transition at T 0 = 171 K. The magnetic susceptibility is nearly isotropic from 2 to 350 K. The heat capacity data gives a Sommerfeld coefficient of 8.2 ± 0.3 mJ mol −1 K −2 , and does not reveal any evidence for the presence of high frequency (>300 K) optical phonon modes. The Hall coefficient is negative below the transition, indicating dominant n-type carriers.