The first antiferroelectric liquid crystal (AFLC) exhibiting a (chiral) nematic phase, a combination which has long been the goal of synthetic chemists working with polar liquid crystals but which at the same time represents a fundamental contradiction in terms of translational order, was recently reported by Nishiyama and co-workers. We have investigated this chiral twin dimer by optic, electrooptic, and dielectric methods and conclude that it is not an ordinary AFLC material, but one where the peculiar properties of bent-core smectics are combined with those of ordinary rod-shaped liquid crystals. The compound exhibits a new type of nematic−smectic phase transition, connected with a change of molecule conformation from rod- to bent-shaped. This also has an important impact on the chiral interactions in the system. Toward the high-temperature end of the smectic phase, the energy balance between bent conformation smectic and straight conformation nematic can be shifted by an electric field such that the t...