Lepton number as a fourth color is the intriguing theoretical idea of the famous Pati-Salam (PS) model. While in conventional PS models, the symmetry breaking scale and the mass of the resulting vector leptoquark are stringently constrained by $K_Ltomu e$ and $Ktopimu e$, the scale can be lowered to a few TeV by adding vector-like fermions. Furthermore, in this case, the intriguing hints for lepton flavour universality violation in $bto smu^+mu^-$ and $bto ctau u$ processes can be addressed. Such a setup is naturally achieved by implementing the PS gauge group in the five-dimensional Randall-Sundrum background. The PS symmetry is broken by boundary conditions on the fifth dimension and the resulting massive vector leptoquark automatically has the same mass scale as the vector-like fermions and all other resonances. We consider the phenomenology of this model in the context of the hints for lepton flavour universality violation in semileptonic $B$ decays. Assuming flavour alignment in the down sector we find that in $bto sell^+ell^-$ transitions the observed deviations from the SM predictions (including $R(K)$ and $R(K^*)$) can be explained with natural values for the free parameters of the model. Even though we find sizable effects in $R(D)$, $R(D^*)$ and $R(J/Psi)$ one cannot account for the current central values in the constrained setup of our minimal model due to the stringent constraints from $D-bar D$ mixing and $tauto 3mu$.
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