  We report large magnetoresistance (MR) and Shubnikov-de Haas (SdH)
oscillations in single crystals of magnetically (M= Ni and Fe) doped
M$_x$Bi$_{0.97-x}$Sb$_{0.03}$ ($x=$ 0, 0.02) topological insulators. The
R$\bar{3}$m symmetry and phase have been confirmed by the Rietveld refinement
of x-ray diffraction data. Interestingly, a magnetic field induced phase
transition from semi-metallic to semi-conducting type is found with the energy
gap around 80 meV at 15 Tesla in the $x=$ 0 sample. Moreover, we observe linear
behavior of MR up to 15 Tesla in transverse mode and SdH oscillations in
longitudinal mode where the field direction is with respect to the current and
crystal plane. For the parent sample, we found the coherence length L$_\phi=$
12.7 nm through the fitting of MR data in transverse mode with modified H-L-N
equation. The extracted frequencies of SdH oscillations using the fast Fourier
transform method and Landau level (LL) fan diagram are found to be consistent
for the parent and Ni doped samples. The determined Fermi surface area is found
to be slightly larger in Ni doped as compared to the parent sample possibly due
to change in the Fermi energy. The Kohler's plot indicates a single scattering
mechanism below 100 K. More importantly, the analysis with the help of LL fan
diagram reveals the non-zero Berry phase $\phi_{\rm B}= -$(1$\pm$0.1)$\pi$,
which demonstrates the non-trivial topological states near the Dirac point in
the parent and Ni doped samples.
