ZURICH, June 6 (Reuters) - Law firm Quinn Emanuel

Urquhart & Sullivan said on Thursday it had filed a lawsuit

against Switzerland in the U.S. District Court for the Southern

District of New York on behalf of a group of Credit Suisse

Additional Tier 1 (AT1) bondholders.

AT1 bonds, which act as a shock absorber if a bank's capital

levels fall below a certain threshold, have been encouraged by

regulators since the 2008-09 global financial crisis.