Large enhancement of the resistive anomaly in the pentatelluride materials<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">HfTe</mml:mi></mml:mrow><mml:mrow><mml:mn>5</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">ZrTe</mml:mi></mml:mrow><mml:mrow><mml:mn>5</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>with applied magnetic field

The resistivity of single-crystal pentatellurides, ${\mathrm{HfTe}}_{5}$ and ${\mathrm{ZrTe}}_{5},$ has been measured as a function of temperature and applied magnetic field. At zero magnetic field these materials exhibit a peak in their resistivity (at ${T}_{P})$ as a function of temperature that corresponds to an, as yet, undetermined phase transition. The application of a transverse magnetic field (B \ensuremath{\perp} to the current I) has a profound effect on the resistive peak in these materials, shifting the peak to slightly higher temperatures and producing a large enhancement of the resistivity at the peak, up to a factor of 3 in ${\mathrm{ZrTe}}_{5}$ ${(T}_{P}=145\mathrm{K})$ and 10 in ${\mathrm{HfTe}}_{5}$ ${(T}_{P}=80\mathrm{K}).$ Larger magnetoresistance is observed at even lower temperatures, $T&lt;20\mathrm{K}.$