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An isomeric state of Hf 177 with T_~_=(1,12_0,10)s was found by a fast chemical separation of the hafnium daughter from the 155 d Lu 177m activity. We measured the sanae half-life by observing the delayed fl-y-coincidences. A systematic investigation of the whole region 5s> T 89 10 -7 s by the technique of delayed coincidences gave no further isomerism. We assign the observed half-life to the ~ three particle state of Hf 177 at 1315 keV and assume that the second hypothetical three particle state at 1337 keV does not exist. The ~1 rotational state of the K=-~ band is populated by a strongly converted 14,16keV y-transition from the isomeric state at 1315 keV. The 14,16 keV M I and N I conversion lines were observed by use of a double focusing magnetic fl-spectrometer. The isomerism is caused by the K-selection rule. The retardation of the following three y-transitions by different degrees of K-forbiddeness is discussed. The pulse height spectrum, measured by means of a Li-drifted Ge-detector, does not show the 36,52 keV-y-transition which was previously assumed topopulate the 1301keVstate. In addition to the known y-transitions we found a 40,9 keV-line. This is probably the transition between the 1301,1 keV and the 1260,3 keV-states.

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