Irish investment vehicle Sealink Funding is suing Citigroup (C) over $513.3 million in residential-mortgage backed securities deals that allegedly contained toxic underlying mortgages. 

The structured-finance investment unit was known at the height of the mortgage bubble for its role in acquiring a slew of RMBS deals.

Sealink Funding has already gone after Citi's fellow big banks, JPMorgan Chase (JPM), Royal Bank of Scotland (RBS) and Bank of America (BAC) for RMBS deals that the investment vehicle believes contained material misrepresentations about the quality of the underlying mortgages.

In the latest suit filed in a New York state court, Sealink suggests Citi and related entities deposited, underwrote, sold and sponsored RMBS deals that contained misrepresented loan-to-value ratios and inaccurate information about the owner-occupancy status of various loans.

Sealink is suing for damages or rescissions on the RMBS transactions.

Citi declined to comment on the case.