It is demonstrated in electro-optic experiments that a uniaxial nematic phase of a bent-core mesogen can be switched into an optically strongly biaxial state by means of an external electric field of the order of 10 5 V/m. The metastable biaxial state is identified by its optical and electric properties. After the field is switched off, uniaxial and biaxial domains can coexist for about one hour. During this time, the biaxial domains gradually shrink but they can be stabilized in moderate

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... ic fields. The formation of inversion walls inside the biaxial domains in the planar ground state, as well as the occurence of such domains in homeotropic cells evidence that the biaxiality is not imposed by the boundary conditions of the planar cell.