Heavy quarks and tau leptons: New physics opportunities

In this talk I discuss the role of heavy quarks in new physics searches with tau leptons. I focus on new physics effects associated to the scalar sector which are naturally enhanced for the heaviest fermions due to the large hierarchy of the fermion masses. I will discuss two topics within this context: lepton flavour violation in the $\tau -\mathrm{\ell }$ ($\mathrm{\ell }=e,\mu$) sector and violations of lepton universality in tauonic $B$ decays.