  The effect of temperature on the crust-core transition of a magnetar is
studied. The thermodynamical spinodals are used to calculate the transition
region within a relativistic mean-field approach for the equation of state.
Magnetic fields with intensities $5\times 10^{16}$ G and $5\times 10 ^{17}$ G
are considered. It is shown that the effect on the extension of the crust-core
transition is washed away for temperatures above $10^{9}$ K for magnetic field
intensities $ \lesssim 5\times 10^{16}$ G but may still persist if a magnetic
field as high as $5\times 10 ^{17}$G is considered. For temperatures below that
value, the effect of the magnetic field on crust-core transition is noticeable
and grows as the temperature decreases and, in particular, it is interesting to
identify the existence of disconnected non-homogeneous matter above the $B=0$
crust core transition density. Models with different symmetry energy slopes at
saturation show quite different behaviors. In particular, a model with a large
slope, as suggested by the recent results of PREX-2, predicts the existence of
up to four disconnected regions of non-homogeneous matter above the zero
magnetic field crust-core transition density.
