CP-odd Neutral Higgs Effects in Top -- anti-Top Production

We study $CP$ violation in the process $e^+e^- \to t\bar{t} \nu\bar{\nu}$ at an $e^+e^-$-TeV collider. As the source of $CP$ violation we assume a two-Higgs doublet model with an explicitly $CP$-noninvariant Higgs potential. Sizeable $CP$-odd observables originating from the subprocess reaction, $W^+W^- \to t\bar{t}$, may arise as a result of finite width effects of the neutral Higgs particles. $CPT$ constraints due to final (initial) state interactions are also taken into account. Numerical estimates of the $CP$ asymmetry are given.