LOS ANGELES -- One of Yahoo! ( YHOO)'s largest shareholders, Ivory Investment Management LP, is urging the Internet company to pursue a sale of its search unit to Microsoft ( MSFT).

In a letter to the company's board, the investment firm proposed a deal Wednesday in which Microsoft would acquire Yahoo's search engine and Yahoo would retain 80% of revenue generated by search queries on its own site.

Ivory proposed Microsoft pay $15 billion for the search platform. It says that would give Yahoo shareholders $24 to $29 per share, well above Yahoo's recent price.

Ivory owns about 1.5% of Yahoo.

Talks between Microsoft and Yahoo about a possible buyout of all of Yahoo fell apart this summer.
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