Fig. 4.

(A) Temperature dependence of thermal conductivity divided by $T$, $\kappa /T$, plotted as a function of $T^2$ in zero field. Magnetic field dependence of $\kappa (H)/T$ for (B) $x=$ 0.08, (C) x = 0.13, (D) x = 0.16, and (E) x = 0.20. The gray arrows indicate $H_{c2}$. Insets show $\kappa /T$ plotted as a function of $\sqrt{{\mu }_{0}H}$. $H\text{*}$ represents a magnetic field at which $\kappa (H)/T$ deviates from the $\sqrt{H}$ dependence. The black arrows in the main panels indicate $H\text{*}$.