Siúcra, Thursday, August 31, at Trilogy in Boulder, is an act with a deceiving handle. Siúcra is an Irish word meaning sugar,: and while this band has certainly mastered Irish music, the sound it creates is anything but sweet. True, the threesome (Beth Leachman on vocals and bodhran, Shannon Heaton on flute and whistle, and Matthew Heaton on guitar) shines on the sort of giddy, raise-up-your-Guinness romps that thrill Green Isle wannabes on St. Paddyís Day. But the group matches its sunny tunes with dark laments, wistful instrumentals and heartbreaking tales that add a delicious edge to its impressive debut disc, A Place I Know. This is the sort of Celtic folk that wins over the Americana crowd -- what Fred Eaglesmith or Lucinda Williams might play if they hailed from Belfast or Dublin. The sound is elevated to heavenly heights by Leachmanís haunting vocals, traditional-style singing that crackles with killer tone and fire. Adding to the bandís gifts are the hot-shot jazzy playing of the husband-and-wife Heatons, who arenít afraid to add a few contemporary American touches to their musical mulligan stew. Sweetness never packed so much spank.