  As the Fermi level and band structure of two-dimensional materials are
readily tunable, they constitute an ideal platform for exploring Lifshitz
transition, a change in the topology of a material's Fermi surface. Using
tetralayer graphene that host two intersecting massive Dirac bands, we
demonstrate multiple Lifshitz transitions and multiband transport, which
manifest as non-monotonic dependence of conductivity on charge density n and
out-of-plane electric fieldD, anomalous quantum Hall sequences and Landau level
crossings that evolve with n, D and B.
