Implementation of the O(αt2) MSSM Higgs-mass corrections in FeynHiggs

We describe the implementation of the two-loop Higgs-mass corrections of O(αt2) in the complex MSSM in FeynHiggs. The program for the calculation is comprised of several scripts which flexibly use FeynArts and FormCalc together with other packages. It is included in FeynHiggs and documented here in some detail so that it can be re-used as a template for similar calculations.