We found three smectic phases, SmX1, SmX2 and SmX3, in achiral compounds with banana shape. The SmX1 phase has a biaxial single molecular layer, along which polarization exists. The polarization precesses along the layer normal, and is aligned by applying an electric field. The spontaneous polarization is about 60 nC/cm(2) and shows a slight temperature dependence. The dielectric constant shows a larger value in SmX1 than those of the other phases, suggesting the Goldstone mode. The relaxation frequency is below 100 Hz.