Leptoquarks and contact interactions at HERA

Leptoquark and Contact Interaction searches have been performed in e±p collisions at HERA at a centre-of-mass energy of 300-320 GeV. The deep inelastic scattering data collected in the years 1994-2005 have been used for searches thus exploiting nearly whole available HERA statistics. No evidence for the leptoquarks was found. The limits from searches of leptoquarks coupling to first generation fermions (lepton flavour conserved) and searches of lepton flavour violation in ep collisions have been derived. The deep inelastic neutral current scattering at high negative four momentum transfer squared Q2 have been used to search for eq contact interactions associated to scales beyond HERA centre-of-mass energy. The neutral current cross section measurements are well described by the Standard Model and are used to set constraints on new phenomena.