  This Letter presents the first search for a heavy particle decaying into an
e\mu final state in sqrt(s)=7 TeV pp collisions at the LHC. The data were
recorded by the ATLAS detector during 2010 and correspond to a total integrated
luminosity of 35/pb. No excess above the Standard Model background expectation
is observed. Exclusions at 95% confidence level are placed on two
representative models. In an R-parity violating supersymmetric model, tau
sneutrinos with a mass below 0.75 TeV are excluded, assuming single coupling
dominance and the couplings lambda'_{311}=0.11, lambda_{312}=0.07. In a lepton
flavor violating model, a Z'-like vector boson with masses of 0.70 to 1.00 TeV
and corresponding cross sections times branching ratios of 0.175 to 0.183 pb is
excluded. These results extend to higher mass RPV sneutrinos and LFV Z's than
previous constraints from the Tevatron.
