  We employ molecular beam epitaxy to stabilize Ba2IrO4 thin films and utilize
in situ angle-resolved photoemission spectroscopy to investigate the evolution
of its electronic structure through the Neel temperature TN. Our measurements
indicate that dispersions of the relativistic Jeff=1/2 and 3/2 bands exhibit an
unusual dichotomy in their behavior through the Neel transition. Although the
charge gap survives into the paramagnetic state, only the Jeff=1/2 state
exhibits a strong temperature dependence and its gap softens with increasing
temperature approaching TN, while the nearly fully occupied Jeff=3/2 state
which remains nearby in energy exhibits negligible changes with temperature.
