  We use our high resolution He-lamp based, tunable laser-based ARPES
measurements and density functional theory calculations to study the electronic
properties of LaBi, a binary system that was proposed to be a member of a new
family of topological semimetals. Both bulk and surface bands are present in
the spectra. The dispersion of the surface state is highly unusual. It
resembles a Dirac cone, but upon closer inspection we can clearly detect an
energy gap. The bottom band follows roughly a parabolic dispersion. The
dispersion of the top band remains very linear, "V" shape like, with the tip
approaching very closely to the extrapolated location of Dirac point. Such
asymmetric mass acquisition is highly unusual and opens a possibility of a new
topological phenomena that has yet to be understood.
