  CaFeAs2 is a parent compound of recently discovered 112-type iron-based
superconductors. It is predicted to be a staggered intercalation compound that
naturally integrates both quantum spin Hall insulating and superconducting
layers and an ideal system for the realization of Majorana modes. We performed
a systematical angle-resolved photoemission spectroscopy and first-principle
calculation study of the slightly electron-doped CaFeAs2. We found that the
zigzag As chain of 112-type iron-based superconductors play a considerable role
in the low-energy electronic structure, resulting in the characteristic
Dirac-cone like band dispersion as the prediction. Our experimental results
further confirm that these Dirac cones only exists around the X but not Y
points in the Brillouin zone, breaking the S4 symmetry at iron sites. Our
findings present the compelling support to the theoretical prediction that the
112-type iron-based superconductors might host the topological nontrivial edge
states. The slightly electron doped CaFeAs2 would provide us a unique
opportunity to realize and explore Majorana fermion physics.
