The rebounding residential-mortgage bond market is facing some resistance.

Redwood Trust (RWT), the leading issuer of mortgage securities backed by loans without government guarantees, is paying investors a yield of about 2.59% to sell its sixth issue of the year, a premium of 1.75 percentage points above an interest-rate benchmark.

Premiums on deals it sold in January were as low as 0.97 percentage point for a yield of less than 2%.