The temperature dependent resistivity of Ba$_{1-x}$K$_x$Fe$_2$As$_2$ (x = 0.23, 0.25, 0.28 and 0.4) single crystals and the angle dependent resistivity of superconducting Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ single crystals were measured in magnetic field
s up to 9 T. The measurements of temperature dependent resistivity for samples with different doping levels revealed very high upper critical fields which increase with the transition temperature monotonously, and a very low superconducting anisotropy ratio $Gamma=H_{c2}^{ab}/H_{c2}^c approx$ 2. By scaling the resistivity in the frame of the anisotropic Ginzburg-Landau theory, the angle dependent resistivity of the Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ single crystal measured with different magnetic fields at a certain temperature collapsed onto one curve. As the only scaling parameter, the anisotropy $Gamma$ was determined alternatively for each temperature and was found to be between two and three.
We report a detailed investigation on the lower critical field $H_{c1}$ of the superconducting Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ (FeAs-122) single crystals. A pronounced kink is observed on the $H_{c1}(T)$ curve, which is attributed to the existence of
two superconducting gaps. By fitting the data $H_{c1}(T)$ to the two-gap BCS model in full temperature region, a small gap of $Delta_a(0)=2.0pm 0.3$ meV and a large gap of $Delta_b(0)=8.9pm 0.4$ meV are obtained. The in-plane penetration depth $lambda_{ab}(0)$ is estimated to be 105 nm corresponding to a rather large superfluid density, which points to the breakdown of the Uemura plot in FeAs-122 superconductors.
