  We study the differential conductance, spectral density and magnetization,
for a quantum dot coupled to two conducting leads as a function of bias
voltage, magnetic field and temperature. The system is modeled with the
Anderson model solved using a spin dependent interpolative perturbative
approximation in the Coulomb repulsion U that conserves the current. For large
enough magnetic field, the differential conductance as a function of bias
voltage shows split peaks. This splitting is larger than the corresponding
splitting in the spectral density of states, in agreement with experiment.
