  The changes a (negative) tidal charge causes at the phenomenon of
superradiance which occurs around rotating black holes are investigated. This
is made by computing the amplification factors of massless scalar waves being
scattered by the black hole. It is shown that the increase of the tidal charge
intensity leads to a considerable enhancement of energy extraction from
near-extreme black holes. Such improvement results from the fact that extreme
black holes with more negative tidal charges spin faster. Maximum amplification
decreases with the increase of the tidal charge intensity if the angular
momentum of the black hole per unit mass is fixed. The tidal charge may also
change crucially the superradiance phenomenon of massless scalar waves causing
maximum amplification to occur for $m > 1$ differently from the case of Kerr
black holes.
