UK neobank Monzo has reached a valuation of $5.9 billion through a secondary market share sale.Existing investors such as Singapore's sovereign wealth fund (GIC) and StepStone Group purchased additional shares in the fintech.The sale provides liquidity for Monzo employees and rewards their contributions to the company's growth.Monzo's valuation has increased since its recent fundraise, and its roadmap includes European expansion and accelerated rollout in the US market.