  Moire materials like twisted bilayer graphene have emerged as a rich
playground of strongly correlated physics, where the effect of interactions can
be drastically enhanced by tuning the non-interacting density of states via
twist angle. A key feature of bilayer graphene at small twist angles is that
the two valleys of graphene are effectively decoupled at the non-interacting
level, leading to an emergent U(1) symmetry corresponding to the conservation
of valley-charge. Theoretical studies invariably find that short-ranged
interactions tend to break this symmetry, leading to inter-valley coherence
(IVC). However, there is no direct experimental probe of this ubiquitous
ordering tendency. Here, I propose an experimental signature of IVC order by
coupling with a closely related system where valley-mixing is guaranteed - the
pentagonal disclinations of graphene. Such disclinations are naturally found in
fullerenes. The tunneling current between twisted bilayer graphene and an
appropriately oriented large buckyball has a sharp signature of the onset of
IVC order. Successfully integrating these fullerenes in a scanning tunneling
microscope would allow spatial resolution of the IVC order parameter on a
sub-moire scale. Experimentally constraining the broken symmetries and order
parameters in the multitude of emerging correlated insulators is a crucial
first step to understanding the superconductivity that develops on doping these
exotic `normal' states.
