Second harmonic generation (SHG) has been studied in a nitro‐substituted ferroelectric liquid crystal cooled from the smectic‐C* into a three‐dimensional crystalline (K) phase in an applied electric field. The SHG efficiency in theKphase is found to bedeff≳4.5 pm/V, about 25 times the value in the SmC* phase, and, unlike the SmC* case, remains constant in zero field for ≳25 h. A quantitative analysis of the polarization dependence of the SHG reveals that the dominantdcoefficients contributing to the measured signal differ for the two phases, and that the orientation of the liquid‐crystal director in theKphase is modulated in one dimension. ©1995 American Institute of Physics.