The invention relates to a spiral curve in elevation comprising a spiral spring formed in a single piece of silicon and coaxially with a ferrule, the spring having a terminal curve of silicon (7) and a lifting device (9) silicon between the outermost convolution (15) of said spiral spring and said terminal curve to form a Breguet spring. According to the invention, the lifting device (9) comprises a mechanical fastener (17) in form of a cross having at least two opposite arms (12) which cooperate with clamping means (23, 25) respectively integral with the curve terminal (7) and the outerwrap (15) of said spiral spring. The invention also relates to the manufacturing process of said hairspring. The invention relates to the field of watch movements.
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