  Electron correlation in a quantum many-body state appears as peculiar
scattering behaviour at its boundary, symbolic of which is Andreev reflection
at a metal-superconductor interface. Despite being fundamental in nature,
dictated by the charge conservation law, however, the process has had no
analogues outside the realm of superconductivity so far. Here, we report the
observation of an Andreev-like process originating from a topological quantum
many-body effect instead of superconductivity. A narrow junction between
fractional and integer quantum Hall states shows a two-terminal conductance
exceeding that of the constituent fractional state. This remarkable behaviour,
while theoretically predicted more than two decades ago but not detected to
date, can be interpreted as Andreev reflection of fractionally charged
quasiparticles. The observed fractional quantum Hall Andreev reflection
provides a fundamental picture that captures microscopic charge dynamics at the
boundaries of topological quantum many-body states.
