Mortgage lender Resimac enjoyed very strong growth in loan settlements and the value of its loan book during the December half, helping the company to a 44 per cent increase in earnings.The company reported that loan settlements increased 22 per cent to A$2.4 billion, compared with the previous corresponding period. Prime loans accounted for $1.7 billion of settlements and specialist loans $700 million.The value of the loan book increased by 20 per cent to $11.3 billion.Resimac made a net profit of $27.2 million for the six months to December - up 44 per cent on the previous corresponding period.Net interest income rose 55 per cent to $84.5 million. The margin rose from 1.48 per cent to 1.83 per cent.On a normalised basis, excluding one-off items, profit rose 85 per cent to $26.9 million.Some other impressive numbers were a return on equity of 26 per cent (up 860 basis points) and a cost-to-income ratio of 42.1 per cent. CTI fell from 57.8 per cent in the previous corresponding period.One negative consequence of the strong growth in lending was a big jump in bad debts. The loan impairment expense rose from $1.6 million in the December 2018 half to $3.8 million in the latest half.On the funding side the company completed three transactions worth a total of $2.5 billion during the half. It also issued in the US 144a market and it is developing distribution in Asia working with UOB, MUFG and SMBC.It stopped originating white label loans during the half. The company announced in December that it would focus on products it funded itself. The white label portfolio (which is not counted as part of the $11.3 billion loan book) fell 11 per cent to $2.9 billion during the half.Resimac is diversifying its business, with a move into asset finance. In December it acquired a controlling interest in asset finance company IA Group. And in July it acquired 15 per cent of Positive Group, another asset finance company.And it is pushing harder into the direct sales channel, with more investment in digital systems.