  Surface of quantum materials often exhibits significantly different behavior
than the bulk due to changed topologies and symmetry protections. The
outstanding problem is to find out if the exoticity of a material is linked to
the changed topology at the surface or it is a bulk property. Hard x-ray
photoemission spectroscopy (HAXPES) is a significantly bulk sensitive technique
(escape depth of valence electrons is about 40 \AA\ for 6 keV photon energy)
and the probing depth can be tuned by changing the electron emission angle.
Therefore, HAXPES is often used to reveal the surface-bulk differences in a
material. Here, we show that the delineation of surface-bulk differences in the
valence band spectral functions using this method is highly non-trivial due to
the complexity arising from linear dichroic effect in addition to the change in
surface sensitivity. We show that core level spectra can be used to reveal the
surface-bulk differences in the electronic structure. The Ca 2p spectra exhibit
evidence of significant hybridization with the conduction electrons revealing
their importance in the electronic properties of the system as also found for
the charge reservoir layers in cuprate superconductors. The Fe 2p core level
spectra as a function of bulk sensitivity and temperature reveals an unusual
scenario; while the surface electronic structure corroborates well with the
observed phase transitions of the system, the bulk spectra exhibit signature of
additional structural phases providing a rare evidence of structural anomaly to
be a bulk property.
