Dec 9 (Reuters) - Digital lender Nubank"s (NU.N) shares opened 25% above the offer price in their stock market debut on Thursday, giving the company a market capitalization of nearly $52 billion, making it the third most valuable listed firm in Brazil. At that valuation, the Sao Paulo-based fintech, backed by Warren Buffett"s Berkshire Hathaway Inc (BRKa.N), is only behind commodities players Petrobras (PETR4.SA) and Vale (VALE3.SA).On Wednesday, Nubank priced its initial public offering at the top end of a range it had lowered earlier due to concerns over a global rout in technology stocks, to raise nearly $2.6 billion. The offer was eight times oversubscribed, one source with knowledge of the matter said. The flotation comes as a record year for U.S. listings, which saw heavyweights like Coinbase (COIN.O) and Robinhood (HOOD.O) go public, draws to a close. Nubank has said it had turned a profit in the first half of 2021 in its Brazilian operations. Founder and Chief Executive Officer David Velez said the company will stay focused on three markets - Brazil, Mexico and Colombia. "A lot of the capital that we"re raising in this IPO is for Colombia and Mexico. And so we will continue to just invest behind that growth opportunity," Velez said in an interview with Reuters. Nubank"s investors include Sequoia Capital, Tiger Global Management and SoftBank Latin America Funds. "Nubank is one of those companies whose shares we might want to hold for the very long term," said Douglas Leone, global managing partner at Sequoia, in an interview with Reuters. Sequoia started investing in Nubank in the seed round in 2013. "Right now the focus is to make sure we (Nubank) do the very best job for customers in Latin America," added Leone, who is also a member of the fintech"s board of directors. Having become one of Brazil"s biggest credit card issuers, Nubank has pioneered products that have spawned off a fierce race among competitors. read more The company"s stock opened at $11.25 per share, compared with the initial public offering price of $9 per share. Morgan Stanley, Goldman Sachs & Co, Citigroup and NuInvest are the lead underwriters for the offering.