Utilize the input text as a context reference, choose the right relationship between Vikram Pandit and Citigroup from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

LONDON, Oct 6 (Reuters) - Former Citigroup Chief Executive Vikram Pandit has taken a stake in London-based currency transfer startup Transferwise, adding to his portfolio of financial technology investments.

Answer: employer