(Bloomberg) -- Treasury-bill yields have risen sharply as a wave of new issuance tests investor demand, posing a threat to the stability of overnight funding markets.That dynamic showed up in the eight-week bill auction this week, with its record-low demand and yields at 4.05%, the highest in over a year — evidence of investor reluctance to pile into the growing supply of bills to fund the widening deficit and an uncertain path of Federal Reserve interest rates over the coming months.