A return to lending growth at AMP Bank over the last six months has gone hand in hand with a further improvement in its net interest margin and a lift in the return on equity.The AMP Bank ROE, at 17.2 per cent, is industry leading if the returns of major banks are any guide. Operating earnings for the bank increased 18 per cent to A$59 million over the half year to June 2016.The interest margin widened to 1.71 per cent from 1.53 per cent.Deposit growth is another bright spot, reaching $10.7 billion, a rise of close to $2 billion.AMP said its return on capital lifted 0.9 percentage points to 17.2 per cent.Rob Caprioli, AMP's group executive for advice and banking, said in the AMP investor report that AMP Bank "continues to grow year on year, with its contribution to group profits doubling during the past five years."Caprioli continued: " There is significant potential to grow the bank further through financial advisers and brokers."