Fixed resistors
https://en.m.wikipedia.org/wiki/Resistor
The TCR of foil resistors is extremely low, and has been further improved over the years. One range of ultra-precision foil resistors offers a TCR of 0.14 ppm/°C, tolerance ±0.005%, long-term stability (1 year) 25 ppm, (3 years) 50 ppm (further improved 5-fold by hermetic sealing), stability under load (2000 hours) 0.03%, thermal EMF 0.1 μV/°C, noise −42 dB, voltage coefficient 0.1 ppm/V, inductance 0.08 μH, capacitance 0.5 pF.

Quantum based resistors :
https://en.m.wikipedia.org/wiki/Quantum_Hall_effect
Quantum Hall effect →
Applications →
Electrical resistance standards :

(...) Later, the 2019 revision of the SI fixed exact values of h and e, resulting in an exact
R~K~ = h/e^2^ = 25812.80745... Ω.

(this is precise to at least 10 significant digits)

Quantum Ampere Standard
https://www.nist.gov/noac/technology/current-and-voltage/quantum-ampere-standard
.
https://www.nist.gov/noac/technology/current-and-voltage

(...) Quantum-based measurements for voltage and current are moving toward greater miniaturization (...)

(there also been research for defining a quantum based volt standard)