  A search is presented for microscopic black holes in a like-sign dimuon final
state in proton--proton collisions at sqrt(s)= 8 TeV. The data were collected
with the ATLAS detector at the Large Hadron Collider in 2012 and correspond to
an integrated luminosity of 20.3 fb-1. Using a high track multiplicity
requirement, 0.6 +- 0.2 background events from Standard Model processes are
predicted and none observed. This result is interpreted in the context of
low-scale gravity models and 95% CL lower limits on microscopic black hole
masses are set for different model assumptions.
