  The propagation of Dirac fermions in graphene through a long-period periodic
potential would result in a band folding together with the emergence of a
series of cloned Dirac points (DPs). In highly aligned graphene/hexagonal boron
nitride (G/hBN) heterostructures, the lattice mismatch between the two atomic
crystals generates a unique kind of periodic structure known as a moir\'e
superlattice. Of particular interests is the emergent phenomena related to the
reconstructed band-structure of graphene, such as the Hofstadter butterfly,
topological currents, gate dependent pseudospin mixing, and ballistic miniband
conduction. However, most studies so far have been limited to the lower-order
minibands, e.g. the 1st and 2nd minibands counted from charge neutrality, and
consequently the fundamental nature of the reconstructed higher-order miniband
spectra still remains largely unknown. Here we report on probing the
higher-order minibands of precisely aligned graphene moir\'e superlattices by
transport spectroscopy. Using dual electrostatic gating, the edges of these
high-order minibands, i.e. the 3rd and 4th minibands, can be reached.
Interestingly, we have observed interband Landau level (LL) crossinginducing
gap closures in a multiband magneto-transport regime, which originates from
band overlap between the 2nd and 3rd minibands. As observed high-order
minibands and LL reconstruction qualitatively match our simulated results. Our
findings highlight the synergistic effect of minibands in transport, thus
presenting a new opportunity for graphene electronic devices.
