Experimental signatures of nodeless multiband superconductivity in a [Formula: see text] single crystal

In order to understand the superconducting gap nature of a [Formula: see text] single crystal with [Formula: see text] , in-plane thermal conductivity [Formula: see text] , in-plane London penetration depth [Formula: see text] , and the upper critical fields [Formula: see text] have been investigated. At zero magnetic field, it is found that no residual linear term [Formula: see text] exists and [Formula: see text] follows a power-law [Formula: see text] (T: temperature) with n = 2.66 at [Formula: see text] , supporting nodeless superconductivity. Moreover, the magnetic-field dependence of [Formula: see text] /T clearly shows a shoulder-like feature at a low field region. The temperature dependent [Formula: see text] curves for both in-plane and out-of-plane field directions exhibit clear upward curvatures near [Formula: see text] , consistent with the shape predicted by the two-band theory and the anisotropy ratio between the [Formula: see text] (T) curves exhibits strong temperature-dependence. All these results coherently suggest that [Formula: see text] is a nodeless, multiband superconductor.