  We investigate electronic transport in high mobility (\textgreater 100,000
cm$^2$/V$\cdot$s) trilayer graphene devices on hexagonal boron nitride, which
enables the observation of Shubnikov-de Haas oscillations and an unconventional
quantum Hall effect. The massless and massive characters of the TLG subbands
lead to a set of Landau level crossings, whose magnetic field and filling
factor coordinates enable the direct determination of the
Slonczewski-Weiss-McClure (SWMcC) parameters used to describe the peculiar
electronic structure of trilayer graphene. Moreover, at high magnetic fields,
the degenerate crossing points split into manifolds indicating the existence of
broken-symmetry quantum Hall states.
