Citigroup has hired Stephanie Mathern, a collateralized debt obligation marketer at Bear Stearns in London, for a similar role marketing both CDOs and credit derivatives. She will report to Neil Servis, head of the London structured credit syndicated and product marketing team. Mathern will start in June. The firm plans to hire another structured professional for the team in the near future. Jeremy Hughes, spokesman at Citigroup, confirmed the moved. Mathern could not be reached.