  In previous studies the pressure dependence of the magnetic ordering
temperature $T_{\text{o}}$ of Dy was found to exhibit a sharp increase above
its volume collapse pressure of 73 GPa, appearing to reach temperatures well
above ambient at 157 GPa. In a search for a second such lanthanide, electrical
resistivity measurements were carried out on neighboring Tb to 141 GPa over the
temperature range 3.8 - 295 K. Below Tb's volume collapse pressure of 53 GPa,
the pressure dependence $T_{\text{o}}(P)$ mirrors that of both Dy and Gd.
However, at higher pressures $T_{\text{o}}(P)$ for Tb becomes highly anomalous.
This result, together with the very strong suppression of superconductivity by
dilute Tb ions in Y, suggests that extreme pressure transports Tb into an
unconventional magnetic state with an anomalously high magnetic ordering
temperature.
