  Highly-doped graphene samples show the conductance reduced and the shot-noise
power enhanced compared to standard ballistic systems in two-dimensional
electron gas. These features can be understood within a model assuming
incoherent scattering of Dirac electrons between two interfaces separating the
sample and the leads. Here we find, by adopting the above-mentioned model for
the edge-free (Corbino) geometry and by means of the computer simulation of
quantum transport, that another graphene-specific feature should be observable
when the current flow through a doped disk is blocked by high magnetic field.
In case the conductance drops to zero, the Fano factor approaches the value of
$F\approx{}0.56$, with a very weak dependence on the disk radii ratio. The role
of finite source-drain voltages and the system behavior upon tuning the
electrostatic potential barrier from a rectangular to parabolic shape are also
discussed.
