Signet Jewelers' (SIG) shares surged after reporting sparkling holiday sales Tuesday, helping boost the company's expectations for Valentine's Day sales. The operator of Kay Jewelers and Jared said U.S. same-store sales, those open at least a year, rose 4.7% during November and December. The holiday season typically accounts for half of Signet's profit and a third of sales. Signet shares jumped 9% intraday Tuesday. Rival high-end retailer Tiffany