  We study an interacting single-level quantum dot weakly coupled to three
electrodes. When two electrodes are biased by voltages with opposite
polarities, while keeping the third lead (the stem) grounded, the current
through the stem is a measure of electron-hole asymmetry of the dot. In this
setup we calculate the stem current for both metallic and ferromagnetic
(collinearly polarized) leads and discuss how the three-terminal device gives
additional information compared to the usual two-terminal setup. We calculate
both the sequential and cotunneling contribution for the currents. For the
latter part we include a regularization procedure for the cotunneling current,
which enables us to also describe the behavior at the charge degeneracy points.
