Switchable Dielectric, Piezoelectric, and Second‐Harmonic Generation Bistability in a New Improper Ferroelectric above Room Temperature

: Imidazolium periodate (IPI) is found to be an improper ferroelectric. It shows bistable properties simultaneously in three channels of dielectricity, piezoelectricity, and second-harmonic generation within the temperature window 300-310 K.