Brazil’s Nu Pagamentos SA, a six-year-old fintech firm that grew to become the nation’s fifth-biggest credit-card issuer, has chosen the next target in its Latin American expansion: Argentina. The firm known as Nubank and backed by Goldman Sachs Group Inc. and Tencent Holdings Ltd. will open an office in the South American nation, co-founder Cristina Junqueira said in an interview. Rafael Soto, former chief executive officer at Argentina’s mobile payments app Uala, will head the new venture. Nubank plans to have 300 employees in Argentina by the end of 2020, Junqueira said. The fintech firm has 9 million customers, and recently sold private shares at a $3.6 billion valuation.