Tandem saw underlying profitability grow five-fold on the previous year, hitting £17.2 million, thanks to a net interest income rise of 28% to £87.8 million.The challenger has repositioned itself as a green alternative to traditional mainstream banks, offering customers loans, savings and mortgage products designed to help them transition to a lower carbon lifestyle.Alex Mollart, chief executive, Tandem, says: “Tandem’s strategy of becoming the UK’s greener, digital bank is working. We’re profitable for a second year running and delivering growth across deposits, lending and revenue - attracting more green-savvy consumers to the bank. “It’s great to see so many customers buying into our mission to help the transition to a lower carbon lifestyle - and save money along the way. We’ve seen big increases in customers trusting their hard-earned savings with Tandem, while helping to fund the green lending we offer to customers looking to switch to a greener lifestyle."