The resonant frequency is the frequency at which the voltage and current are in phase. This is not necessarily the frequency at which the maximum impedance occurs. At the resonant frequency, the imaginary component of the impedance will be zero, but the magnitude of the impedance will not necessarily be maximum.
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In the circuit proposed by LvW, there is indeed a minimum that occurs at a frequency well below the resonant frequency and the frequency of maximum impedance.
Regards,
Kral