  When Bloch electrons in a solid are exposed to a strong optical field, they
are coherently driven in their respective bands where they acquire a quantum
phase as the imprint of the band shape. If an electron approaches an avoided
crossing formed by two bands, it may be split by undergoing a Landau-Zener
transition. We here employ subsequent Landau-Zener transitions to realize
strong-field Bloch electron interferometry (SFBEI), allowing us to reveal band
structure information. In particular, we measure the Fermi velocity (band
slope) of graphene in the vicinity of the K points as (1.07$\pm$0.04) nm
fs$^{-1}$. We expect SFBEI for band structure retrieval to apply to a wide
range of material systems and experimental conditions, making it suitable for
studying transient changes in band structure with femtosecond temporal
resolution at ambient conditions.
