Upper critical fields and superconducting anisotropy of K 0.70 Fe 1.55 Se 1.01 S 0.99 and K 0.76 Fe 1.61 Se 0.96 S 1.04 single crystals

We have investigated temperature and angular dependence of resistivity of K 0.70(7) Fe 1.55(7) Se 1.01(2) S 0.99(2) and K 0.76(5) Fe 1.61(5) Se 0.96(4) S 1.04(5) single crystals. The upper critical fields μ 0 H c 2 ( T ) for both field directions decrease with the increase in S content. On the other hand, the angle-dependent magnetoresistivity for both compounds can be scaled onto one curve using the anisotropic Ginzburg-Landau theory. The obtained anisotropy of μ 0 H c 2 ( T ) increases with S content, implying that S doping might decrease the dimensionality of certain Fermi surface parts, leading to stronger two-dimensional character.