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We have observed Shubnikov-de Haas oscillations in the longitudinal magnetoresistance of SnTe, a cubically symmetric, extrinsic ptype semiconductor. 1 " 5 The measurements were made in steady magnetic fields up to 155 kG. Oscillations were detected between 40 and 155 kG, and were seen in samples with carrier concentrations 6 /) between 5xl0 19 and 5xl0 20 cm" 3 . It is very unusual to have observed the Shubnikov-de Haas effect over such a wide range of carrier concentrations. Moreover, the upper limit is some 25 times larger than the highest concentration at which such oscillations have been detected previously in an extrinsic material. 7 It was possible to observe the oscillations at such large carrier concentrations because of the high magnetic field intensities available, and because of the extraordinarily weak "ionized impurity" scattering 8 in SnTe.The results presented here already suggest (1) the orientation of the Fermi surfaces, (2) the presence of a second, lower-lying valence band, and (3) an explanation for several puzzling electrical and elastic measurements obtained earlier. 2 ' 6 ' 9For our as-pulled single crystals, />«5xl0 20 cm"" 3 . We obtained lower p values by diffusion techniques to be described elsewhere. The crystallographic orientations studied included [001], [114], [112], [111], and [110] directions. Measurements were made at 4.2 and 1.4°K. The high, steady magnetic fields were produced in a li-inch inner diameter modified Bitter-type solenoid. 10

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Laser calorimetric or thermal rise techniques are useful for the determination of very low absorption coefficients in solids. A number of improvements in this technique are described of which the most important is a means of separating surface and bulk absorption. These techniques have been applied to study alkali halides in the ir but are applicable where laser sources of sufficient power are available.

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