composition Rb$_{0.90}$Fe$_{1.78}$Se$_2$.

As the crystals are sensitive to air, all sample preparations were preformed inside a nitrogen-flushed glove box. ARPES measurements were carried out at beamline 10.0.1 of the Advanced Light Source and beamline 5-4 of Stanford Synchrotron Radiation Lightsource using SCIENTA R4000 electron analyzers. The total energy resolution used was 25 meV or better and the angular resolution was 0.3$^\circ$C. Single crystals were cleaved in situ at low temperatures and measured in an ultra high vacuum chamber with a base pressure better than $3x10^{-11}$ Torr.

Discussion of orbital assignment
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The common band structure for FeSC in the Brillouin zone (BZ) corresponding to the two-Fe unit cell consists of three hole bands near the $\Gamma$ point and two electron bands at the X point [@s2graser]. Under C$_4$ rotational symmetry, the [$d_{xz}$]{} and [$d_{yz}$]{} bands are degenerate at the in-plane high symmetry points of the BZ-$\Gamma$ and X points. At the $\Gamma$ point, this means that the [$d_{xz}$]{} and [$d_{yz}$]{} hole bands must be degenerate. Hence we have assigned the two lower degenerate hole bands in Fig. \[fig:fig1\]e to [$d_{xz}$/$d_{yz}$]{} and the higher one to [$d_{xy}$]{}. At the X point, C$_4$ symmetry dictates the bottom of the [$d_{xz}$/$d_{yz}$]{} electron band 