  Conductivity of monolayer and two-layer graphene is considered with due
regard for mutual drag of band electrons and holes. Search of contribution of
the drag in conductivity shows that this effect can sufficiently influence on
mobility of carriers, which belong to different groups and have different drift
velocities. In two-layer system the mutual drag can even change the di-rection
of partial current in separate layer.

Mesoscale and Nanoscale Physics