  Magnetic fields can be generated in plasmas by the Biermann battery when the
electric field produced by the electron pressure gradient has a curl. The
commonly employed magnetohydrodynamic (MHD) model of the Biermann battery
breaks down when the electron distribution function is distorted away from
Maxwellian. Using both MHD and kinetic simulations of a laser-plasma
interaction relevant to inertial confinement fusion we have shown that this
distortion can reduce the Biermann-producing electric field by around 50\%.
More importantly, the use of a flux limiter in an MHD treatment to deal with
the effect of the non-Maxwellian electron distribution on electron thermal
transport leads to a completely unphysical prediction of the Biermann-producing
electric field and so results in erroneous predictions for the generated
magnetic field.
