Quantum dots with even number of electrons: Kondo effect in a finite magnetic field

We show that the Kondo effect can be induced by an external magnetic field in quantum dots with an even number of electrons. If the Zeeman energy B is close to the single-particle level spacing Δ in the dot, the scattering of the conduction electrons from the dot is dominated by an anisotropic exchange interaction. A Kondo resonance then occurs despite the fact that B exceeds by far the Kondo temperature T_K. As a result, at low temperatures T ≪ T_K the differential conductance approaches a unitary limit G_K ∼ e²/πħ. A possible experimental realization of this effect is discussed.