  The zero gap surface states of a 3D-topological insulator host Dirac fermions
with spin locked to the momentum. The gap-less Dirac fermions exhibit
electronic behaviour different from those predicted in conventional materials.
While calculations based on a simple linear dispersion can account for observed
experimental patterns, a more accurate match is obtained by including higher
order $ \overrightarrow{k}$ terms in the Hamiltonian. In this work, in presence
of a time reversal symmetry breaking external magnetic field and higher order
warping term, alteration to the topologically ordained Berry phase of $ (2n +
1)\pi $, momentum relaxation time, and the magneto-conductivity tensors is
established.
