  We study transport through a lateral quantum dot in the vicinity of the
singlet-triplet transition in its ground state. This transition, being sharp in
an isolated dot, is broadened to a crossover by the exchange interaction of the
dot electrons with the conduction electrons in the leads. For a generic set of
system's parameters, the linear conductance has a maximum in the crossover
region. At zero temperature and magnetic field, the maximum is the strongest.
It becomes less pronounced at finite Zeeman splitting, which leads to an
increase of the background conductance and a decrease of the conductance in the
maximum.
