Type-I superconductivity in YbSb2 single crystals

We present evidence of type-I superconductivity in YbSb2 single crystals from dc and ac magnetization, heat capacity, and resistivity measurements. The critical temperature and critical field are determined to be T-c approximate to 1.3 K and H-c approximate to 55 Oe. A small Ginzburg-Landau parameter kappa = 0.05, together with typical magnetization isotherms of type-I superconductors, small critical field values, a strong differential paramagnetic effect signal, and a field-induced change from second- to first-order phase transition, confirms the type-I nature of the superconductivity in YbSb2. A possible second superconducting state is observed in the radio-frequency susceptibility measurements, with T-c((2)) approximate to 0.41 K and H-c((2)) approximate to 430 Oe.