  A sterile neutrino with mass of several keV is a well-motivated dark-matter
candidate, and it can also explain the observed velocities of pulsars via
anisotropic emission of sterile neutrinos from a cooling neutron star. We
discuss the interactions of such relic particles with matter and comment on the
prospects of future direct detection experiments. A relic sterile neutrino can
interact, via sterile-active mixing, with matter fermions by means of
electroweak currents, with the final state containing a relativistic active
neutrino. The recoil momentum impacted onto a matter fermion is determined by
the sterile neutrino mass and is enough to ionize atoms and flip the spins of
nuclei. While this suggests a possibility of direct experimental detection, we
calculate the rates and show that building a realistic detector of the required
size would be a daunting challenge.
