  The outer crust structure and composition of a cold, non-accreting magnetar
is studied. We model the outer crust to be made of fully equilibrated matter
where ionized nuclei form a Coulomb crystal embedded in an electron gas. The
main effects of the strong magnetic field are those of quantizing the electron
motion in Landau levels and of modifying the nuclear single particle levels
producing, on average, an increased binding of nucleons in nuclei present in
the Coulomb lattice. The effect of an homogeneous and constant magnetic field
on nuclear masses has been predicted by using a covariant density functional,
in which induced currents and axial deformation due to the presence of a
magnetic field that breaks time-reversal symmetry have been included
self-consistently in the nucleon and meson equations of motion. Although not
yet observed, for $B\gtrsim 10^{16}$G both effects contribute to produce
different compositions and to enlarge the range of pressures typically present
in common neutron stars. Specifically, in such a regime, the magnetic field
effects on nuclei favor the appearance of heavier nuclei at low pressures. As
$B$ increases, such heavier nuclei are also preferred up to larger pressures.
In the most extreme case, the whole outer crust is almost made of
${}_{40}^{92}$Zr$_{52}$.
