Russian Academy of Sciences, an outstanding scientist and a recognized authority in semiconductor physics died on October 30, 2001. Isaak Mikha|̄lovich Tsidil'kovski|̄ was born on May 21, 1923 in the Rakitno village of the Kiev region in the family of a teacher. He lived his childhood and school years in the town of Belaya Tserkov' and, having graduated from secondary school in 1940, enrolled in theKiev Industrial Institute. Great Patriotic War began as I M Tsidil'kovski|̄ had just passed his exams for the first year, and he immediately volunteered to the front. In the Army in the Field he soldiered in the infantry, in the battle reconnaissance, and as a radio operator; he retreated with the army all the long way from the banks of the Dnepr river to Stalingrad and theKalmykia steppes, and then retraced the long trek as occupied Ukraine and Belorussia were liberated; he took part in the Warsaw operation, and in the storms ofKoÈ nigsberg and Berlin. The last shots of the war sounded when he was in Prague. During the long four years at the front line, he was wounded twice and was several times seriously shell-shocked. In later life, he courageously resisted the consequences of these wounds. After demobilization, I M Tsidil'kovski|̄ continued his studies at the Physics Department of Kiev State University. His student years coincided with the start of rapid progress in semiconductor physics. Brilliant lectures and colloquia by Professors V E Loshkarev and S I Pekar determined Tsidil'kovski|̄'s choice of the field of research. The initial work done in his student years (experimental study of photoconductivity and a solution of problems in the theory of transport phenomena) was typical of the scientific style of Isaak Mikha|̄lovich: he invariably combined thorough preparation of an experiment with a profound theoretical interpretation of the results obtained. I M Tsidil'kovski|̄ found his own path in physics with his first independent steps made in the Dagestan Branch of the USSR Academy of Sciences in Makhachkala. On the advice of Academician A F Ioffe he began a study of thermomagnetic phenomena in semiconductors. He had to go through every stage of the basic work required of an experimenter Ð from growing his samples to building his measuring installations. In five years he was able to study a surprisingly broad class of semiconducting materials. Professor Vladimir Pantele|̄monovich Zhuze, one of the pioneers of semiconductor physics and known for his encyclopedic erudition and extensive experimental experience, worked in Makhachkala at the time and played an important role in Tsidil'kovski|̄'s growth as a mature scientist. Isaak Mikha|̄lovich was deeply grateful to Vladimir Pantele|̄monovich all his life and dedicated one of his latest monographs, Effective Mass Concept (1999), to this unforgettable personality. The pioneering work on the physics of thermomagnetic phenomena in semiconductors that I M Tsidil'kovski|̄ has done in the 1950s proved conclusively all the advantages of these effects employed as subtle tools in studying the mechanisms of charge carrier scattering in solids. The novel field of solid state kinetics was born largely owing to this work of IMTsidil'kovski|̄. Five years of research were summarized in his monograph Thermomagnetic Phenomena in Semiconductors (1959), the first literature in the world in this field; it was immediately translated into English and is important for researchers even today. In 1957, the then Corresponding Member of the USSR Academy of Sciences S V Vonsovski|̄ invited I M Tsidil'kovski|̄ to remove to Sverdlovsk and fill a position at the Institute of Metal Physics. Here in 1960 I M Tsidil'kovski|̄ organized the Laboratory of Semiconductors and SemimeUspekhi Fizicheskikh Nauk 172 (7) 839 ± 840 (2002) Translated by V I Kisin PERSONALIA PACS number: 01.60.+q