Identification of a phason heat capacity in the low-temperature specific heat of potassium

The low-temperature specific heat of potassium has been remeasured in the temperature range 0.5-5 K. An anomaly located around 1 K is identified as a phason-heat-capacity contribution. The fraction of phonons converted to phasons is 2×${10}^{-5\mathrm{}}$ and the Debye temperature of these phasons is 6 K. Two independent measurements of the same potassium sample show a difference of 2% in total specific heat but both sets show the same phason anomaly around 1 K.