June 18 (Reuters) - Shares of Atai Life Sciences B.V., backed by billionaire investor Peter Thiel, jumped 40% in their U.S. stock market debut on Friday, giving the German psychedelics startup a market capitalization of $3.19 billion. Reporting by Sohini Podder and Niket Nishant in Bengaluru; Editing by Devika Syamnath Our Standards: The Thomson Reuters Trust Principles.