Differential cross section as a function of $\it{p}_{\rm{T, KK}}^{\rm{2}}$ for exclusive \KK photoproduction in Pb--Pb UPCs at \mbox{$\sqrt{s_{\rm{NN}}}$= 5.02 \TeV} and $|y_{\rm{KK}}|0.8$. The vertical lines and boxes across the data points represent statistical and systematic uncertainties, respectively. The dashed blue line and band are the result of a fit to an exponential with the fixed slope parameter \mbox{$b=428\ \pm\ 6\ ({\rm stat.})\ \pm\ 15\ ({\rm syst.})$ \inverseGeVcSquared,} from a previous result on $\rho^{0}$ production~ (see the text for details). The inset shows two curves from STARlight with and without interference between the two photon directions~.