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We report the discovery from our IRSF/SIRIUS Near-Infrared (NIR) variabilitysurvey of five new classical Cepheids located in the inner Galactic Disk, atlongitude $l\simeq -40^{\circ}$. The new Cepheids are unique in probing thekinematics and metallicity of young stars at the transition between the innerDisk and the minor axis of the central Bar, where they are expected to be lessaffected by its dynamical influence.This is also the first time thatmetallicity of Cepheids is estimated on the basis of medium-resolution($R\sim3,000$) NIR spectra, and we validated our results with data in theliterature, finding a minimal dependence on the adopted spectroscopicdiagnostics. This result is very promising for using Cepheids as stellar proxyof the present-time chemical content of the obscured regions in the Disk. Wefound that the three Cepheids within 8--10 kpc from us have metallicitiesconsistent with the mean radial metallicity gradient, and kinematics consistentwith the Galactic rotation curve. Instead, the closest ($\sim$4 kpc)/farthest($\sim$12 kpc) Cepheids have significant negative/positive residuals, both invelocity and in iron content. We discuss the possibility that such residualsare related to large-scale dynamical instabilities, induced by thebar/spiral-arm pattern, but the current sample is too limited to reach firmconclusions.

First metallicity determination from Near-Infrared spectra for five obscured Cepheids discovered in the inner Disk