Like Mehmet, at least 8 percent of Turkish adults do not have a bank account for religious reasons, according to a 2014 World Bank report, because of the prohibition in Islam against paying interest. Under President Tayyip Erdogan, an authoritarian leader with roots in Islamist politics and an aversion to usury, Turkey is hoping it can turn disdain for traditional banks among the pious into a boom in Islamic finance, where, instead of interest, banks charge service fees and depositors share in bank profits.