  The zero-temperature magnetic field-dependent conductance of electrons
through a one-dimensional non-interacting tight-binding chain with an
interacting {\it side} dot is reviewed and analized further. When the number of
electrons in the dot is odd, and the Kondo effect sets in at the impurity site,
the conductance develops a wide minimum as a function of the gate voltage,
being zero at the unitary limit. Application of a magnetic field progressively
destroys the Kondo effect and, accordingly, the conductance develops pairs of
dips separated by $U$, where $U$ is the repulsion between two electrons at the
impurity site. Each one of the two dips in the conductance corresponds to a
perfect spin polarized transmission, opening the possibility for an optimum
spin filter. The results are discussed in terms of Fano resonances between two
interfering transmission channels, applied to recent experimental results, and
compared with results corresponding to the standard substitutional
configuration, where the dot is at the central site of the non-interacting
chain.
