  In this contribution we report on the calculation of the next-to-leading
order (NLO) QCD corrections to the hadro-production of heavy neutral Higgs
bosons and their decay into top-quark pairs within the type-II
two-Higgs-doublet extension of the standard model (SM). We take into account
the contributions from resonant Higgs boson production, the non-resonant SM
$t\bar{t}$ background as well as the interference of these two contributions.
The NLO corrections to the signal and interference contributions are calculated
by applying the heavy top-quark mass ($m_t$) limit including an effective
rescaling. In our NLO calculation the QCD-Higgs interference is evaluated in
the resonance region that provides the dominant part of the heavy Higgs-boson
contributions. Evaluating representative $CP$-conserving and $CP$-violating
parameter scenarios within the two-Higgs-doublet model (2HDM) we present
results for different distributions and, in addition, for observables that
depend on the top-quark spin.
