India, March 6 -- Finance minister Nirmala Sitharaman on Friday indicated the government's intent to appeal against an arbitration panel asking India to return $1.4 billion to UK's Cairn Energy Plc, saying it is her "duty" to appeal in cases where the nation's sovereign authority to tax is questioned. Last year, the government lost two arbitrations against British firms, using legislation that gave it the power to levy taxes with retrospective effect. While the government has already challenged an international arbitration tribunal verdict that overturned its demand for Rs.22,100 crore in back taxes from Vodafone Group, it hasn't yet done so against an award to adjust a Rs.10,247 crore tax demand on Cairn. "...if there is a question about t...