  An electrically charged black hole solution with scalar hair in four
dimensions is presented. The self-interacting scalar field is real and it is
minimally coupled to gravity and electromagnetism. The event horizon is a
surface of negative constant curvature and the asymptotic region is locally an
AdS spacetime. The asymptotic fall-off of the fields is slower than the
standard one. The scalar field is regular everywhere except at the origin, and
is supported by the presence of electric charge which is bounded from above by
the AdS radius. In turn, the presence of the real scalar field smooths the
electromagnetic potential everywhere. Regardless the value of the electric
charge, the black hole is massless and has a fixed temperature. The entropy
follows the usual area law. It is shown that there is a nonvanishing
probability for the decay of the hairy black hole into a charged black hole
without scalar field. Furthermore, it is found that an extremal black hole
without scalar field is likely to undergo a spontaneous dressing up with a
nontrivial scalar field, provided the electric charge is below a critical
value.
