  Magnetic tunnel junctions with the layer sequence
Co$_2$Cr$_{0.6}$Fe$_{0.4}$Al/MgO/CoFe were fabricated by magnetron sputtering
at room temperature (RT). The samples exhibit a large inverse tunneling
magnetoresistance (TMR) effect of up to -66% at RT. The largest value of -84%
at 20 K reflects a rather weak influence of temperature. The dependence on the
voltage drop shows an unusual behavior with two almost symmetric peaks at
$\pm600$ mV with large inverse TMR ratios and small positive values around zero
bias.
