We present measurements of the magneto-thermopower fluctuations of a gate-d
efined, chaotic quantum dot in a (Al,Ga)As-semiconductor heterostructure. C
urrent-heating techniques were employed to build up the necessary temperatu
re difference across the quantum dot for the thermopower measurement. A sta
tistical ensemble is generated by registering the magnetic-field and gate-v
oltage dependence for a number of slightly different dot sizes. The experim
ental results are in good agreement with the predicted non-gaussian distrib
ution of the Random Matrix Theory. To our knowledge these are the first tra
nsport experiments that directly yield the non-gaussian distribution which
are an unambiguous sign for the occurence of chaos. (C) 1998 Elsevier Scien
ce B.V. All rights reserved.