  We explain recent LHCb measurements of the lepton universality ratios,
$R_{D^{(*)}}^{\tau/\ell}\equiv \frac{\mathcal{B}(\bar B \to D^{(*)+} \tau^-
\bar\nu_\tau)} {\mathcal{B}(\bar B \to D^{(*)+}\ell^- \bar\nu_\ell)}$ and
${R(\Lambda_c^+)}^{\tau/\ell} \equiv \frac{\mathcal{B}(\Lambda_b \to
\Lambda_c^+ \tau^- \bar{\nu}_{\tau})}{\mathcal{B}(\Lambda_b \to \Lambda_c^+
\ell^- \bar{\nu}_{\ell})}$ with $\ell=\mu$, via new physics that affects
$R_D^{\tau/\ell}$ and $R(\Lambda_c^+)^{\tau/\ell}$ but not
$R_{D^*}^{\tau/\ell}$. The scalar operator in the effective theory for new
physics is indicated. We find that the forward-backward asymmetry and $\tau$
polarization in $\bar{B} \to D^+ \tau^{-} \bar{\nu}_{\tau}$ and $\Lambda_b \to
\Lambda_c^+ \tau^- \bar{\nu}_{\tau}$ decays are significantly affected by the
scalar interaction. We construct a simple two Higgs doublet model as a
realization of our scenario and consider lepton universality in semileptonic
charm and top decays, radiative $B$ decay, $B$-mixing, and $Z \to b \bar b$.
