  We study the sensitivity of top polarization observables to the CP phase
$\zeta_t$ in the top Yukawa coupling in the process $pp\to thj$ at the 14 TeV
high-luminosity run of the Large Hadron Collider (HL-LHC). We calculate the top
polarization in this process as well as an azimuthal asymmetry of the charged
lepton arising from the decay of the top in the lab frame. We find that the
dependence of this lab-frame azimuthal asymmetry on the phase $\zeta_t$ closely
resembles the dependence of the top polarization on $\zeta_t$. As compared to
the cross section, which is sensitive to $\zeta_t$ for larger values, the
lepton azimuthal asymmetry can provide a sensitive measurement of $\zeta_t$ for
smaller values.
