  We report our study of the I-V curves in the transport through the quantum
dot when an additional quantum dot lying in the Kondo regime is side-connected
to it. Due to the Kondo scattering off the effective spin on a side-connected
quantum dot the conductance is suppressed at low temperatures and at low
source-drain bias voltages. This zero-bias anomaly is understood as enhanced
Kondo scattering with decreasing temperature.
