SAN FRANCISCO (REUTERS) - Square will purchase buy now, pay later (BNPL) firm Afterpay for about US$29 billion (S$39.3 billion) in Australia's biggest-ever buyout, creating an online payments giant to tap explosive growth in the niche payments sector. Afterpay has been the bellwether of the niche online payments sector, which burst into the mainstream last year as more people, especially youngsters, chose to pay in instalments for everyday items during the pandemic. Burgeoning popularity, quick uptake among users and relatively loose regulation has led to rapid growth in the sector, and has reportedly even driven Apple to plan a service to let shoppers pay for purchases in instalments. "Square and Afterpay have a shared purpose... together, we can better connect our Cash App and Seller ecosystems to deliver even more compelling products and services for merchants and consumers," Square chief executive Jack Dorsey said. For Afterpay, the deal provides an opportunity to expand rapidly in the United States, where its fiscal 2021 sales nearly tripled to A$11.10 billion (S$11 billion) in constant currency. The news also comes at a time of frenzied deal-making activity in Australia. Afte...