  We report on a novel material obtained by modifying pristine YBCO
superconductor in solid phase synthesis via simultaneous partial substitution
of Ba by Sr and O by Se. Simultaneous application of EDX and EBSD confirmed
that Se atoms indeed enter the crystalline lattice cell. The detailed XRD
analysis further confirmed this conclusion and revealed that the obtained
polycrystalline material contains 5 phases, with the major phase ($>$30\%)
being a cuprate YBa$_{1.4}$Sr$_{0.6}$Cu$_{3}$O$_{6}$Se$% _{0.51}$. The obtained
superconductor demonstrates unique properties, including i) two superconducting
transitions with $T_{c1}\approx$ 35 K (granular surface phase) and
$T_{c2}\approx$ 13 K (bulk granular phase) - this granular phase arrangement
naturally yields the Wohlleben effect; ii) reentrant diamagnetism and resistive
state; iii) strong paramagnetism with Curie-Weiss behavior (% $\theta_{CW}
\approx$ 4 K) and the ferromagnetic phase overruled by superconductivity; iv)
Schottky anomaly visible in the heat capacity data and most likely delivered by
small clusters of magnetic moments. Thorough analysis of the heat capacity data
reveals a strong-coupling $d-$wave pairing in its bulk phase (with $2\Delta
/T_{c}\approx 5$), and, most importantly, a very unusual anomaly in this
cuprate. There are reasons to associate this anomaly with the quantum
criticality observed in traditional cuprate superconductors at much higher
fields (achievable only in certain laboratories). In our case, the fields
leading to quantum criticality are much weaker ($\sim $7-9 T) thus opening
avenues for exploration of the interplay between superconductivity and pair
density waves by the wider research community.
