Searching New Physics in Muonium Atom
  Quantum Electrodynamics describes electromagnetic interactions of free muons and of muon and electron in the muonium atom to very high accuracy. Contributions of other and yet unknown interactions can be investigated in precision experiments, e.g. by searching for muonium-antimuonium conversion and by measuring the muon magnetic anomaly. 
K.Jungmann (Physikalisches Institut, Universitaet Heidelberg,   Heidelberg, Germany)