  We investigate bulk and holographic features of finite-temperature black
brane solutions of 4D anti-de Sitter Einstein-Maxwell-dilaton-gravity (EMDG).
We construct, numerically, black branes endowed with non trivial scalar hairs
for broad classes of EMDG. We consider both exponential and power-law forms for
the coupling functions, as well as several charge configurations: purely
electric, purely magnetic and dyonic solutions. At finite temperature the field
theory holographically dual to these black brane solutions has a rich and
interesting phenomenology reminiscent of electron motion in metals: phase
transitions triggered by nonvanishing VEV of scalar operators, non-monotonic
behavior of the electric conductivities as function of the frequency and of the
temperature, Hall effect and sharp synchrotron resonances of the conductivity
in presence of a magnetic field. Conversely, in the zero temperature limit the
conductivities for these models show a universal behavior. The optical
conductivity has a power-law behavior as a function of the frequency, whereas
the DC conductivity is suppressed at small temperatures.
